Methods of treating hepatic encephalopathy

ABSTRACT

The application describes treatment of hepatic encephalopathy using gastrointestinal specific antibiotics. One example of a gastrointestinal specific antibiotic is rifaximin.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/768,617, filed Feb. 15, 2013, which is a continuation of U.S.application Ser. No. 13/077,373, filed Mar. 31, 2011, which claimsbenefit of International Patent Application PCT/US2009/059321, filedOct. 2, 2009, which claims benefit of U.S. Provisional Application No.61/102,349, filed Oct. 2, 2008. The entire contents of each of theaforementioned applications are hereby expressly incorporated herein byreference.

BACKGROUND

Hepatic encephalopathy (HE) is caused by a reversible decrease inneurologic function associated with liver failure and portosystemicvenous shunting. HE occurs in 1 of every 3 cases of cirrhosis, in casesof fulminant hepatic failure reported in the United States (US), and ispresent in nearly half of patients reaching end-stage liver disease. Itmay occur at any age, but the peaks parallel those of fulminant liverdisease (peak=40's), and cirrhosis (peak=late 50's).

The incidence of HE is likely to increase with the incidence ofhepatitis C in the general population and cirrhotics in aging patients.Acute HE signifies a serious prognosis with a 40% likelihood of survivalfor 1 year. There is a need in the art for a compositions and methodsfor treating and preventing HE.

SUMMARY

Provided herein are compositions and methods for the prevention andtreatment of hepatic encephalopathy.

One embodiment is a method of treating or preventing hepaticencephalopathy (HE) in a subject comprising administering to a subject agastrointestinal (GI) specific antibiotic. In one embodiment the GIspecific antibiotic is rifaximin. In another embodiment, the rifaximinis 1100 mg/day of rifaximin.

Another embodiment is a method of decreasing a subject's risk of ahepatic encephalopathy HE breakthrough episode by administering a GIspecific antibiotic to a subject suffering from HE.

Yet another embodiment is a method of maintaining remission of hepaticencephalopathy in a subject by administering a GI specific antibiotic toa subject suffering from HE.

Still another embodiment is a method of reducing the frequency ofhospitalization visits by an HE patient, comprising administering a GIspecific antibiotic to a subject suffering from HE.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a line graph comparing lactulose daily use between subjectstaking placebos and subjects taking rifaximin.

FIG. 2 is a line graph showing Kaplan Meier estimates of thedistribution of time to a breakthrough HE event.

FIG. 3 is a line graph showing Kaplan Meier estimates of thedistribution of time to a first HE related hospitalization.

FIG. 4 is a line graph showing Kaplan Meier estimates of thedistribution of time to a first increase in Conn scores.

FIG. 5 is a line graph showing Kaplan Meier estimates of thedistribution of time to a first increase in an Asterixis grade.

FIG. 6 depicts the time to first breakthrough overt he episode (up to 6months of treatment, day 170 in the first study) (ITT Population).

FIG. 7 is a comparison of time to first breakthrough overt he episode inthe first study (rifaximin versus placebo groups) and the second study(new to rifaximin group).

FIG. 8 depicts a comparison of time to first breakthrough overt heepisode during placebo experience (the first study) and after crossoverto rifaximin experience (the second study) among the first study placebosubjects who started rifaximin in the second study.

FIG. 9 depicts the time to first he-related hospitalization (up to 6months of treatment, day 170, in the first study).

FIG. 10 depicts the time to first HE-caused hospitalization in the firststudy (ITT population).

FIG. 11 depicts the time to First Increase in Conn Score (up to 6 monthsof treatment, day 170, the first study) (ITT Population).

FIG. 12 depicts the time to first Increase in asterixis grade (up to 6months of treatment, day 170, the first study) (ITT Population).

FIG. 13 depicts the Kaplan Meier estimates of distribution of time tofirst breakthrough HE for continuing rifaximin subjects who did not havean HE episode in the first study vs placebo.

DETAILED DESCRIPTION

The main pathogenesis of HE is related to nitrogenous substances derivedfrom the gut adversely affecting brain function. The most influential ofthese compounds is thought to be ammonia, a byproduct of proteindigestion that is normally detoxified by the liver. Correlation of bloodlevels with mental state in cirrhosis, however, is inaccurate, in part,because the blood-brain barrier permeability to ammonia is increased inpatients with HE. Other gut-derived toxins have also been proposed asbeing responsible for HE.

In patients with chronic liver disease, the occurrence of hepaticencephalopathy is associated with a low quality of life compared toage-matched patients without HE. Overt HE episodes are debilitating, canpresent without warning, render the patient incapable of self-care, andfrequently result in hospitalization. Patients with HE experiencesymptoms including fatigue, daytime sleepiness, and lack of awareness(Conn score 1); and confusion and disorientation (Conn score 2) thatsignificantly interfere with day-to-day function and decreased abilityfor self care. Often, this lack of self care leads to improper nutritionand non-adherence to therapy and further escalates into more severesymptoms such as increased somnolence, gross disorientation and stupor(Conn score 3) or coma (Conn score 4).

A history of overt HE episodes and the severity of HE episodes were alsofound to be predictive of decreased survival in patients with chronicliver disease. In patients with liver cirrhosis and a history of overtHE episodes, survival probability was 42% at 1 year and 23% at 3 yearsafter experiencing an HE episode. In another analysis, the occurrence ofan HE episode of Conn score 2 in patients with cirrhosis was associatedwith a 4-fold increase in the risk of death.

These toxic compounds gain access to the systemic circulation as aresult of decreased hepatic function or portal-systemic shunts. Once inbrain tissue, the compounds produce alterations of neurotransmissionthat affect consciousness and behavior. HE is attributed to globalcentral nervous system depression from nitrogenous compounds that resultin excitation of gamma-aminobutyric acid (GABA) and decreasedneurotransmission of glutamate.

Precipitating factors include azotemia (29%), sedatives, tranquilizers,analgesics (24%), gastrointestinal bleeding (18%), excess dietaryprotein (9%), metabolic alkalosis (11%), infection (3%), constipation(3%). Surgery, particularly transjugular intrahepatic portal-systemicshunt (TIPS) procedures, also may precipitate HE. HE due to unknowncauses accounts for only 2% of cases.

Initial manifestations are subclinical and require psychometric testingfor diagnosis. There are 4 progressive stages of impairment known as theWest Haven criteria (or Conn score) which range from Stage 0 (Lack ofdetectable changes in personality) to Stage 4 (Coma, decerebrateposturing, dilated pupils) as discussed in more detail below.

HE is manifested as a continuum of psychomotor dysfunction, impairedmemory, increased reaction time, sensory abnormalities, poorconcentration and in severe forms, as coma. Changes may be observed inpersonality, consciousness, behavior and neuromuscular function.Neurologic signs may include hyperreflexia, rigidity, myoclonus andasterixis (coarse “flapping” muscle tremor). Cognitive tasks such asconnecting numbers with lines can be abnormal. Fetor hepaticus (sweetbreath odor) may be present. Electroencephalogram (EEG) tracings shownonspecific slow, triphasic wave activity mainly over the frontal areas.Prothrombin time may be prolonged and not correctable with Vitamin K. Acomputed tomography scan of the head may be normal or show generalatrophy. Finally, signs of liver disease such as jaundice and ascitesmay be noted.

Diagnosis of HE is made on the basis of medical history, and physicaland mental status examinations with the required clinical elements beingknowledge of existent liver disease, precipitating factor(s), and/orprior history of HE. An EEG may show slow-wave activity, even in mildcases. An elevated serum ammonia level is characteristic but notessential, and correlates poorly with the level of encephalopathy

Management of patients with chronic HE includes 1) provision ofsupportive care, 2) identification and removal of precipitating factors,3) reduction of nitrogenous load from the gut, and 4) assessment of theneed for long term therapy. The nitrogenous load from the gut istypically reduced using non-absorbable disaccharide (lactulose) and/orantibiotics.

Lactulose is considered a first-line treatment in the United States, butis not currently approved in the U.S. for either the treatment orprevention of HE. Lactulose is metabolized by the intestinal bacteria ofthe colon, which leads to reduced fecal pH, then to a laxative effect,and finally to fecal elimination. The reduced fecal pH ionizes ammonia(NH₃) to the ammonium ion (NH₄ ⁺) which is used by the bacteria foramino acid and protein synthesis. This lowers the serum ammonia levelsand improves mental function.

Conventional therapy aims to lower the production and absorption ofammonia. Lactulose is typically used in doses of 30-60 g daily. However,the dose can be titrated up to 20-40 g TID-QID to affect 2-3 semi-formedbowel movements per day. If lactulose cannot be administered orally orper nasogastric tube, for example to patients with stage 3 and 4 HE, itmay be given as a 300 cc (200 g) retention enema.

For acute encephalopathy, lactulose can be administered either orally,by mouth or through a nasogastric tube, or via retention enemas. Theusual oral dose is 30 g followed by dosing every 1 to 2 hours untilevacuation occurs. At that point, dosing is adjusted to attain two orthree soft bowel movements daily.

Lactulose for is readily available over-the-counter. A convenient andrelatively tasteless formulation, often referred to in the trade as“lactulose powder for oral solution” can be obtained, for example, fromBertek Pharmaceuticals, Sugarland, Tex. as Kristalose® in 10 and 20 gmpackets. The lactulose syrups commonly sold as laxatives includeCephulac®, Chronulac®, Cholac®, and Enulose®. These syrups can besubstituted for lactulose powder by using sufficient syrup to providethe desired dosage of lactulose; typically, the named syrups containabout 10 gm lactulose in 15 ml of syrup.

Broad-spectrum, GI-active antibiotics including neomycin, metronidazole,vancomycin and paromomycin have been used with or without lactulose.Current guidelines recommend neomycin at 1 to 2 g/day by mouth withperiodic renal and annual auditory monitoring or metronidazole at 250.Lactulose can induce diarrhea leading to dehydration, a precipitatingfactor of HE. Additionally, compliance with lactulose is limited bypatient dislike of its overly sweet taste. In addition, a dosingschedule that is linked to bowel habits and side effects of flatulence,bloating, diarrhea (which leads to dehydration), and acidosis makelactulose difficult to use long-term.

Antibiotic use in treatment of HE is hampered by toxicity associatedwith long-term use. Specifically, systemic absorption of neomycin,metronidazole and ampicillin has led to rare cases of nephrotoxicity,ototoxicity, S. enterocolitis, and/or development of resistant bacterialstrains. Additionally, neomycin inhibits only aerobic bacteria.Metronidazole is metabolized slowly in patients with hepaticdysfunction, has a potential for alcohol interactions (disulfiram-likeeffect), and high blood levels may result in seizures.

One gastrointestinal specific antibiotic is rifaximin. Rifaximin is anonaminoglycoside, semisynthetic antibiotic derived from rifamycin O. Itis a non-systemic, non-absorbed, broad-spectrum, oral antibioticspecific for enteric pathogens of the GI tract. Rifaximin was found tobe advantageous in treatment of HE relative to previously usedantibiotics; e.g., negligible systemic absorption (<0.4%) regardless offood intake or presence of GI disease and exhibits no plasmaaccumulation with high or repeat doses. The lack of systemic absorptionmakes rifaximin safe and well tolerated, thus improving patientcompliance and reducing side effects associated with currently knowntreatments.

Rifaximin (INN; see The Merck Index, XIII Ed., 8304) is an antibioticbelonging to the rifamycin class of antibiotics, e.g., a pyrido-imidazorifamycin. Rifaximin exerts its broad antibacterial activity, forexample, in the gastrointestinal tract against localizedgastrointestinal bacteria that cause infectious diarrhea, irritablebowel syndrome, small intestinal bacterial overgrowth, Crohn's disease,and/or pancreatic insufficiency. It has been reported that rifaximin ischaracterized by a negligible systemic absorption, due to its chemicaland physical characteristics (Descombe J. J. et al. Pharmacokineticstudy of rifaximin after oral administration in healthy volunteers. IntJ Clin Pharmacol Res, 14 (2), 51-56, (1994)).

Rifaximin is described in Italian Patent IT 1154655 and EP 0161534. EPpatent 0161534 discloses a process for rifaximin production usingrifamycin 0 as the starting material (The Merck Index, XIII Ed., 8301).U.S. Pat. No. 7,045,620 B1 discloses polymorphic forms of rifaximin. Theapplications and patents referred to here are incorporated herein byreference in their entirety for all purposes

A rifamycin class antibiotic is, for example, a compound having thestructure of Formula I:

wherein A may be the structure A₁:

-   -   or the structure A₂

wherein, -x- is a covalent chemical bond or nil; R is hydrogen oracetyl;

R₁ and R₂ independently represent hydrogen, (C₁₋₄) alkyl, benzyloxy,mono- and di-(C₁₋₃)alkylamino-(C₁₋₄)alkyl, (C₁₋₃)alkoxy-(C₁₋₄)alkyl,hydroxymethyl, hydroxy-(C₂₋₄)-alkyl, nitro or R₁ and R₂ taken togetherwith two consecutive carbon atoms of the pyridine nucleus form a benzenering unsubstituted or substituted by one or two methyl or ethyl groups;R₃ is a hydrogen atom or nil; with the proviso that, when A is A₁, -x-is nil and R₃ is a hydrogen atom; with the further proviso that, when Ais A₂, -x- is a covalent chemical bond and R₃ is nil.

Also described herein is a compound as defined above, wherein A is A₁ orA₂ as above indicated, -x- is a covalent chemical bond or nil, R ishydrogen or acetyl, R₁ and R₂ independently represent hydrogen,(C₁₋₄)alkyl, benzyloxy, hydroxy-(C₂₋₄)alkyl,di-(C₁₋₃)alkylamino-(C₁₋₄)alkyl, nitro or R₁ and R₂ taken together withtwo consecutive carbon atoms of the pyridine nucleus form a benzene ringand R₃ is a hydrogen atom or nil; with the proviso that, when A is A₁,-x- is nil and R₃ is a hydrogen atom; with the further proviso that,when A is A₂, -x- is a covalent chemical bond and R₃ is nil.

Also described herein is a compound as defined above, wherein A is A₁ orA₂ as above indicated, -x- is a covalent chemical bond or nil, R isacetyl, R₁ and R₂ independently represent hydrogen, (C₁₋₄)alkyl or R₁and R₂ taken together with two consecutive carbon atoms of the pyridinenucleus form a benzene ring and R₃ is a hydrogen atom or nil; with theproviso that, when A is A₁, -x- is nil and R₃ is a hydrogen atom; withthe further proviso that, when A is A₂, -x- is a covalent chemical bondand R₃ is nil.

Also described herein is a compound as defined above, which is4-deoxy-4′-methyl-pyrido[1′,2′-1,2]imidazo[5,4-c]rifamycin SV. Alsodescribed herein is a compound as defined above, which is4-deoxy-pyrido[1′,2′:1,2]imidazo[5,4-c]rifamycin SV.

Also described herein is a compound as defined above, wherein A is asdescribed above, -x- is a covalent chemical bond or nil; R is hydrogenor acetyl; R₁ and R₂ independently represent hydrogen, (C₁₋₄)alkyl,benzyloxy, mono- and di-(C₁₋₃)alkylamino(C₁₋₄)alkyl,(C₁₋₃)alkoxy-(C₁₋₄)alkyl, hydroxymethyl, hydroxy-(C₂₋₄)-alkyl, nitro orR₁ and R₂ taken together with two consecutive carbon atoms of thepyridine nucleus form a benzene ring unsubstituted or substituted by oneor two methyl or ethyl groups; R₃ is a hydrogen atom or nil; with theproviso that, when A is A₁, -x- is nil and R₃ is a hydrogen atom; withthe further proviso that, when A is A₂, -x- is a covalent chemical bondand R₃ is nil.

Rifaximin is a compound having the structure of formula II:

In certain embodiments, the antibiotic comprises one or more of arifamycin, aminoglycoside, amphenicol, ansamycin, β-Lactam, carbapenem,cephalosporin, cephamycin, monobactam, oxacephem, lincosamide,macrolide, polypeptide, tetracycline, or a 2,4-diaminopyrimidine classantibiotic. Exemplary antibiotics of these classes are listed below.

Rifaximin exerts a broad antibacterial activity in the gastrointestinaltract against localized gastrointestinal bacteria that cause infectiousdiarrhea, including anaerobic strains. It has been reported thatrifaximin is characterized by a negligible systemic absorption, due toits chemical and physical characteristics (Descombe J. J. et al.Pharmacokinetic study of rifaximin after oral administration in healthyvolunteers. Int J Clin Pharmacol Res, 14 (2), 51-56, (1994)).

Without wishing to be bound by any particular scientific theories,rifaximin acts by binding to the beta-subunit of the bacterialdeoxyribonucleic acid-dependent ribonucleic acid (RNA) polymerase,resulting in inhibition of bacterial RNA synthesis. It is active againstnumerous gram (+) and (−) bacteria, both aerobic and anaerobic. In vitrodata indicate rifaximin is active against species of Staphylococcus,Streptococcus, Enterococcus, and Enterobacteriaceae. Bacterial reductionor an increase in antimicrobial resistance in the colonic flora does notfrequently occur and does not have a clinical importance. Rifaximin iscurrently approved in 17 countries outside the US and was licensed bythe Food and Drug Administration (FDA) for the US in May 2004.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention as claimed. In thisapplication, the use of the singular includes the plural unlessspecifically stated otherwise. In this application, the use of “or”means “and/or” unless stated otherwise. Furthermore, the use of the term“including”, as well as other forms, such as “includes” and “included”,is not limiting. Also, terms such as “element” or “component” encompassboth elements and components comprising one unit and elements andcomponents that comprise more than one subunit unless specificallystated otherwise. Also, the use of the term “portion” can include partof a moiety or the entire moiety.

All documents, or portions of documents, cited in this application,including but not limited to patents, patent applications, articles,books, and treatises, are hereby expressly incorporated by reference intheir entirety for any purpose.

One embodiment is a method of treating or preventing hepaticencephalopathy (HE) by administering a therapeutically effective amountof a gastrointestinal (GI) specific antibiotic to a subject. Examples ofgastrointestinal antibiotics as used herein include rifamycin classantibiotics, such as rifaximin.

Embodiments of the invention relate to the discovery of the efficacy ofgastrointestinal (GI) specific antibiotics for the treatment andprevention of Hepatic Encephalopathy. Embodiments relate to the use ofGI specific antibiotics to prevent the onset of HE symptoms and also tolengthen the time to a first breakthrough HE episode. In one embodiment,the time to a first breakthrough HE episode was measured by an increaseof the Conn score to Grade ≧2 (e.g., 0 or 1 to ≧2) or a Conn andasterixis score increase of one grade each for those subjects that havea baseline Conn Score of 0. In another embodiment, the time tobreakthrough HE episode was measured by the time to any increase frombaseline in either the Conn score (mental state grade) or asterixisgrade, with Kaplan-Meier estimates of cumulative proportions of subjectswith any increase at Days 28, 56, 84, 112, 140, and 168.

Another embodiment was a measurement of the time to a first HE-relatedhospitalization or the time to development of spontaneous bacterialperitonitis (SBP). Another embodiment was a mean change from baseline inblood ammonia concentration over time or a mean change from baseline incritical flicker frequency values over time. An additional embodimentwas indicated by a mean daily lactulose consumption over time, shiftsfrom baseline in Conn scores over time; or shifts from baseline inasterixis grades over time. Unless otherwise specified, a shift of avalue is the change of that value from a baseline value.

Other measures of efficacy of the treatments described herein includedmean change from baseline in Chronic Liver Disease Questionnaire (CLDQ)scores over time; mean change from baseline in Epworth Sleepiness Scalescores over time; and proportion of subjects who have an EpworthSleepiness Scale score >10. The evaluation of severity of persistenthepatic encephalopathy may also be based, for example, on Conn scores.

In another embodiment, a subject suffering from, susceptible to or inremission from hepatic encephalopathy (HE) can be administered arifamycin class antibiotic for between about 24 weeks and 24 months. Intreating HE, the rifamycin class antibiotic may be administered to thesubject for 12 months and longer, for example for a subject's entirelife span. In one embodiment, the antibiotic is administered daily untilthe death of the subject.

In one embodiment, the invention relates to a method of decreasing asubject's risk of having a breakthrough event by administering to thesubject a GI specific antibiotic. In one embodiment, the for subjectshaving a last HE episode equal to or greater than 90 days prior tostarting on treatment, the risk of failure occurrence was reduced by58%. In another embodiment, the risk of failure occurrence was reducedby between about 30-70%. In another embodiment, the risk was reduced byabout 40% to 70%.

In one embodiment, for subjects having a last HE episode more than 90days prior to administration of a GI specific antibiotic, the risk offailure occurrence was decreased by between about 60%. In anotherembodiment, the risk of failure occurrence was decreased by betweenabout 2%-80%.

In another embodiment, for subjects having two or fewer HE episodes inthe six months prior to starting on treatment, the risk of abreakthrough HE episode was decreased by about a 56%. In one embodiment,the risk of a breakthrough HE episode was decreased by between about a20%-70%.

In another embodiment, for subjects having greater than two HE episodesin the six months prior to starting on treatment, the risk of abreakthrough HE episode was reduced by about 63%. In another embodiment,the risk was reduced by about 30%-80%.

In one embodiment, the therapeutically effective amount of agastrointestinal (GI) specific antibiotic comprises from between about1000 mg to about 1200 mg/day.

In one embodiment, the therapeutically effective amount of agastrointestinal (GI) specific antibiotic comprises from between about1100 mg to about 1200 mg/day.

According to one embodiment, the therapeutically effective amount of agastrointestinal (GI) specific antibiotic comprises about 1150 mg/day.

In another embodiment, the therapeutically effective amount is a dosageregimen of one capsule or tablet of the formulation two times each day,wherein each tablet comprises about 550 mg of the gastrointestinal (GI)specific antibiotic, such as rifaximin.

In one embodiment, the therapeutically effective amount is a dosageregimen of two capsules or tablets three times each day, wherein eachcapsule comprises about 200 mg of the gastrointestinal (GI) specificantibiotic.

In one embodiment, the therapeutically effective amount is a dosage of275 mg of a gastrointestinal (GI) specific antibiotic administered fourtimes per day. In another embodiment, 275 mg of a gastrointestinal (GI)specific antibiotic is administered as two dosage forms two times perday.

Another embodiment is a method of maintaining remission of HE in asubject by administering a GI specific antibiotic to the subject.

Another embodiment is a method of increasing time to hospitalization fortreatment of HE by administering to the subject a GI specificantibiotic. In one embodiment, the administration of a GI specificantibiotic reduces hospitalization frequency by about 48%. In anotherembodiment, a GI specific antibiotic reduces hospitalization frequencyby from between about 13% to about 69%.

In one embodiment, treatment with the gastrointestinal (GI) specificantibiotic maintains remission of HE in the subject.

In one embodiment, the GI specific antibiotic is administered to thesubject for six months, one year, two to three years or daily until thesubject's death.

In one embodiment, a Conn score for the subject is improved overbaseline following administration of a GI specific antibiotic.

In one embodiment, a quality of life (QoL) measurement is improved frombaseline with administration of a GI specific antibiotic over a courseof treatment with rifaximin.

In one embodiment, the GI specific antibiotic is administered to thesubject with lactulose, prior to treatment with lactulose, or followingtreatment with lactulose.

In one embodiment, the GI specific antibiotic is administered with oneor more of align, alinia, Lactulose, pentasa, cholestyramine,sandostatin, vancomycin, lactose, amitiza, flagyl, zegerid, prevacid, ormiralax.

In one embodiment, following treatment with GI specific antibiotic, aConn score (mental state grade) of a subject decreases.

In one embodiment, following treatment with a GI specific antibiotic, aConn score increase from baseline is increased.

In one embodiment, following treatment with a GI specific antibiotic, adelay in time to an increase in Conn score is about 54%. For example,the percentage delay in time to increase in Conn score may be betweenabout 30% to about 70%.

In another embodiment, administration of the GI specific antibioticprevents an increase in Conn score. For example, administration of theGI specific antibiotic increases the time to an increase from baselinein a Conn score.

In one embodiment, administration of the GI specific antibiotic resultsin an increase of time to an increase from baseline in an asterixisgrade.

In another embodiment, administration of the GI specific antibioticresults in a delay in the time to increase in asterixis grade.

In another embodiment, administration of the GI specific antibioticresults in an increase in time to first HE-related hospitalization.

In another embodiment, administration of the GI specific antibioticresults in an increase in the time to development of spontaneousbacterial peritonitis (SBP).

In another embodiment, administration of the GI specific antibioticresults in a decrease in blood ammonia concentration from baseline afteradministration of rifaximin. For example, the decrease in blood ammoniaconcentration may be from baseline to 170 days of about 6 μg/dL.

In another embodiment, administration of the GI specific antibioticresults in an increase in critical flicker frequency values frombaseline after administration of rifaximin.

In another embodiment, administration of the GI specific antibioticresults in a decrease in daily lactulose consumption from baseline overtime after administration with rifaximin.

In another embodiment, administration of the GI specific antibioticresults in a decrease in daily lactulose consumption is from betweenabout 7 doses of lactulose to about 2 doses of lactulose.

In another embodiment, administration of the GI specific antibioticresults in a lactulose use that initially increases from baseline. Forexample, the lactulose use may be from between about 1 and about 30days.

In another embodiment, administration of the GI specific antibioticresults in a shift in baseline in Conn scores over time afteradministration of rifaximin. For example, the shift in baseline in Connscores may be from between about 1 to about 2.

In another embodiment, administration of the GI specific antibioticresults in a shift from baseline in asterixis grades over time.

In another embodiment, administration of the GI specific antibioticresults in a change from baseline in Chronic Liver Disease Questionnaire(CLDQ) scores over time.

In another embodiment, administration of the GI specific antibioticresults in a change from baseline in Epworth Sleepiness Scale scoresover time after administration of rifaximin.

As is known, the Model for End-Stage Liver Disease (MELD) score can beutilized to predict liver disease severity based on serum creatinine,serum total bilirubin, and the international normalized ratio forprothrombin time INR. The MELD score and has been shown to be useful inpredicting mortality in patients with compensated and decompensatedcirrhosis. The maximum score given for MELD is 40. All values higherthan 40 are given a score of 40.

In another embodiment, subjects having a MELD level of between about 1to 24 responded to treatment for HE using administration of the GIspecific. In another embodiment, subjects having a MELD level less thanor equal to 10 responded to treatment with GI specific antibiotics. Inanother embodiment, subjects having a MELD level between 11 and 18respond to treatment with GI specific antibiotics. In anotherembodiment, subjects having a MELD level between 19 and 24 respond totreatment with GI specific antibiotics.

One embodiment of the invention is a method of treating or preventing HEby administering 1100 mg of rifaximin per day to a patient for more than28 days.

Another embodiment is a method of decreasing lactulose use in a subject.This method includes: administering rifaximin to a subject daily that isbeing treated with lactulose, and tapering lactulose consumption. Forexample, the lactulose consumption may be reduced by 1, 2, 3, 4, 5, 6 ormore unit dose cups of lactulose from a baseline level. Alternatively,the lactulose use may be reduced by 5, 10, 15, 20, 25, 30, 34, 40, 45,50, 55, 60, 65, or 70 g lactulose from a baseline level. In oneembodiment, the baseline use of lactulose is no use.

One embodiment of the invention is a method of maintaining remission ofHE in a subject comprising administering 550 mg of rifaximin twice a day(BID) to the subject.

Another embodiment is a method of increasing time to hospitalization fortreatment of HE comprising, administering to a subject 550 mg ofrifaximin two times per day (BID).

The term “administration” or “administering” includes routes ofintroducing a GI specific antibiotic to a subject to perform theirintended function. Examples of routes of administration that may be usedinclude injection (subcutaneous, intravenous, parenterally,intraperitoneally, intrathecal), oral, inhalation, rectal andtransdermal. The pharmaceutical preparations may be given by formssuitable for each administration route. For example, these preparationsare administered in tablets or capsule form, by injection, inhalation,eye lotion, eye drops, ointment, suppository, etc. administration byinjection, infusion or inhalation; topical by lotion or ointment; andrectal by suppositories. Oral administration is preferred. The injectioncan be bolus or can be continuous infusion. Depending on the route ofadministration, a GI specific antibiotic can be coated with or disposedin a selected material to protect it from natural conditions that maydetrimentally effect its ability to perform its intended function. A GIspecific antibiotic can be administered alone, or in conjunction witheither another agent or agents as described above or with apharmaceutically-acceptable carrier, or both. A GI specific antibioticcan be administered prior to the administration of the other agent,simultaneously with the agent, or after the administration of the agent.Furthermore, a GI specific antibiotic can also be administered in aproform, which is converted into its active metabolite, or more activemetabolite in vivo.

Administration “in combination with” one or more further therapeuticagents includes simultaneous (concurrent) and consecutive administrationin any order.

As will be readily apparent to one skilled in the art, the useful invivo dosage to be administered and the particular mode of administrationwill vary depending upon the age, weight and mammalian species treated,the particular compounds employed, and the specific use for which thesecompounds are employed. The determination of effective dosage levels,that is the dosage levels necessary to achieve the desired result, canbe accomplished by one skilled in the art using routine pharmacologicalmethods. Typically, human clinical applications of products arecommenced at lower dosage levels, with dosage level being increaseduntil the desired effect is achieved.

As used herein, an “increase” or “decrease” in a measurement, unlessotherwise specified, is typically in comparison to a baseline value. Forexample, an increase in time to hospitalization for subjects undergoingtreatment may be in comparison to a baseline value of time tohospitalization for subjects that are not undergoing such treatment. Insome instances an increase or decrease in a measurement can be evaluatedbased on the context in which the term is used.

“Carriers” as used herein include pharmaceutically acceptable carriers,excipients, or stabilizers which are nontoxic to the cell or mammalbeing exposed thereto at the dosages and concentrations employed. Oftenthe physiologically acceptable carrier is an aqueous pH bufferedsolution. Examples of physiologically acceptable carriers includebuffers such as phosphate, citrate, and other organic acids;antioxidants including ascorbic acid; low molecular weight (less thanabout 10 residues) polypeptide; proteins, such as serum albumin,gelatin, or immunoglobulins; hydrophilic polymers such aspolyvinylpyrrolidone; amino acids such as glycine, glutamine,asparagine, arginine or lysine; monosaccharides, disaccharides, andother carbohydrates including glucose, mannose, or dextrins; chelatingagents such as EDTA; sugar alcohols such as mannitol or sorbitol;salt-forming counterions such as sodium; and/or nonionic surfactantssuch as TWEEN, polyethylene glycol (PEG).

The term “effective amount” includes an amount effective, at dosages andfor periods of time necessary, to achieve the desired result, e.g.,sufficient to treat or prevent HE in a patient or subject. An effectiveamount of a GI specific antibiotic may vary according to factors such asthe disease state, age, and weight of the subject, and the ability of aGI specific antibiotic to elicit a desired response in the subject.Dosage regimens may be adjusted to provide the optimum therapeuticresponse. An effective amount is also one in which any toxic ordetrimental effects (e.g., side effects) of a GI specific antibiotic areoutweighed by the therapeutically beneficial effects.

“Ameliorate,” “amelioration,” “improvement” or the like refers to, forexample, a detectable improvement or a detectable change consistent withimprovement that occurs in a subject or in at least a minority ofsubjects, e.g., in at least about 2%, 5%, 10%, 15%, 20%, 25%, 30%, 40%,50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, 98%, 100% or in a range betweenabout any two of these values. Such improvement or change may beobserved in treated subjects as compared to subjects not treated withrifaximin, where the untreated subjects have, or are subject todeveloping, the same or similar disease, condition, symptom or the like.Amelioration of a disease, condition, symptom or assay parameter may bedetermined subjectively or objectively, e.g., self assessment by asubject(s), by a clinician's assessment or by conducting an appropriateassay or measurement, including, e.g., a quality of life assessment, aslowed progression of a disease(s) or condition(s), a reduced severityof a disease(s) or condition(s), or a suitable assay(s) for the level oractivity(ies) of a biomolecule(s), cell(s) or by detection of HEepisodes in a subject. Amelioration may be transient, prolonged orpermanent or it may be variable at relevant times during or after a GIspecific antibiotic is administered to a subject or is used in an assayor other method described herein or a cited reference, e.g., withintimeframes described infra, or about 1 hour after the administration oruse of a GI specific antibiotic to about 28 days, or 1, 3, 6, 9 monthsor more after a subject(s) has received such treatment.

The “modulation” of, e.g., a symptom, level or biological activity of amolecule, or the like, refers, for example, that the symptom oractivity, or the like is detectably increased or decreased. Suchincrease or decrease may be observed in treated subjects as compared tosubjects not treated with a GI specific antibiotic, where the untreatedsubjects have, or are subject to developing, the same or similardisease, condition, symptom or the like. Such increases or decreases maybe at least about 2%, 5%, 10%, 15%, 20%, 25%, 30%, 40%, 50%, 60%, 70%,75%, 80%, 85%, 90%, 95%, 98%, 100%, 150%, 200%, 250%, 300%, 400%, 500%,1000% or more or within any range between any two of these values.Modulation may be determined subjectively or objectively, e.g., by thesubject's self assessment, by a clinician's assessment or by conductingan appropriate assay or measurement, including, e.g., quality of lifeassessments or suitable assays for the level or activity of molecules,cells or cell migration within a subject. Modulation may be transient,prolonged or permanent or it may be variable at relevant times during orafter a GI specific antibiotic is administered to a subject or is usedin an assay or other method described herein or a cited reference, e.g.,within times descried infra, or about 1 hour of the administration oruse of a GI specific antibiotic to about 3, 6, 9 months or more after asubject(s) has received a GI specific antibiotic.

The term “modulate” may also refer to increases or decreases in theactivity of a cell in response to exposure to a GI specific antibiotic,e.g., the inhibition of proliferation and/or induction ofdifferentiation of at least a sub-population of cells in an animal suchthat a desired end result is achieved, e.g., a therapeutic result of GIspecific antibiotic used for treatment may increase or decrease over thecourse of a particular treatment.

The term “obtaining” as in “obtaining a GI specific antibiotic” isintended to include purchasing, synthesizing or otherwise acquiring a GIspecific antibiotic.

The phrases “parenteral administration” and “administered parenterally”as used herein includes, for example, modes of administration other thanenteral and topical administration, usually by injection, and includes,without limitation, intravenous, intramuscular, intraarterial,intrathecal, intracapsular, intraorbital, intracardiac, intradermal,intraperitoneal, transtracheal, subcutaneous, subcuticular,intraarticulare, subcapsular, subarachnoid, intraspinal and intrasternalinjection and infusion.

The language “a prophylactically effective amount” of a compound refersto an amount of a GI specific antibiotic which is effective, upon singleor multiple dose administration to the subject, in preventing ortreating HE.

The term “pharmaceutical agent composition” (or agent or drug) as usedherein refers to a chemical compound, composition, agent or drug capableof inducing a desired therapeutic effect when properly administered to apatient. It does not necessarily require more than one type ofingredient.

The compositions may be in the form of tablets, capsules, powders,granules, lozenges, liquid or gel preparations. Tablets and capsules fororal administration may be in a form suitable for unit dose presentationand may contain conventional excipients. Examples of these are: bindingagents such as syrup, acacia, gelatin, sorbitol, tragacanth, andpolyvinylpyrrolidone; fillers such as lactose, sugar, maize-starch,calcium phosphate, sorbitol or glycine; tableting lubricants, such asmagnesium stearate, silicon dioxide, talc, polyethylene glycol orsilica; disintegrants, such as potato starch; or acceptable wettingagents, such as sodium lauryl sulfate. The tablets may be coatedaccording to methods well known in normal pharmaceutical practice. Oralliquid preparations may be in the form of, for example, aqueous or oilysuspensions, solutions, emulsions, syrups or elixirs, or may bepresented as a dry product for reconstitution with water or othersuitable vehicle before use. Such liquid preparations may containconventional additives such as suspending agents, e.g., sorbitol, syrup,methyl cellulose, glucose syrup, gelatin, hydrogenated edible fats,emulsifying agents, e.g., lecithin, sorbitan monooleate, or acacia;non-aqueous vehicles (including edible oils), e.g., almond oil,fractionated coconut oil, oily esters such as glycerine, propyleneglycol, or ethyl alcohol; preservatives such as methyl or propylp-hydroxybenzoate or sorbic acid, and, if desired, conventionalflavoring or coloring agents.

The phrases “systemic administration,” “administered systemically,”“peripheral administration,” and “administered peripherally,” as usedherein mean the administration of a GI specific antibiotic, drug orother material, such that it enters the subject's system and, thus, issubject to metabolism and other like processes, for example,subcutaneous administration.

The language “therapeutically effective amount” of a GI specificantibiotic refers to an amount of a GI specific antibiotic which iseffective, upon single or multiple dose administration to the subject,in inhibiting the bacterial growth and/or invasion, or in decreasingsymptoms, such as HE episodes, relating to bacterial growth in asubject. “Therapeutically effective amount” also refers to the amount ofa therapy (e.g., a composition comprising a GI specific antibiotic),which is sufficient to reduce the severity of HE in a subject.

As used herein, the terms “prevent,” “preventing,” and “prevention”refer to the prevention of the recurrence, onset, or development HEepisodes or more symptoms of HE. Preventing includes protecting againstthe occurrence and severity of HE episodes.

As used herein, the term “prophylactically effective amount” refers tothe amount of a therapy (e.g., a composition comprising a GI specificantibiotic) which is sufficient to result in the prevention of thedevelopment, recurrence, or onset of HE episodes or to enhance orimprove the prophylactic effect(s) of another therapy.

“Rifaximin”, as used herein, includes solvates and polymorphous forms ofthe molecule, including, for example, α, β, γ, δ, ε, η, ξ and amorphousforms of rifaximin. These forms are described in more detail, forexample, in U.S. Ser. No. 11/873,841; U.S. Ser. No. 11/658,702; EP 05004 635.2, filed 3 May 2005; U.S. Pat. No. 7,045,620; U.S. 61/031,329;and G. C. Viscomi, et al., CrystEngComm, 2008, 10, 1074-1081 (April2008). Each of these references is hereby incorporated by reference inentirety.

“Polymorphism”, as used herein, refers to the occurrence of differentcrystalline forms of a single compound in distinct hydrate status, e.g.,a property of some compounds and complexes. Thus, polymorphs aredistinct solids sharing the same molecular formula, yet each polymorphmay have distinct physical properties. Therefore, a single compound maygive rise to a variety of polymorphic forms where each form hasdifferent and distinct physical properties, such as solubility profiles,melting point temperatures, hygroscopicity, particle shape, density,flowability, compactibility and/or x-ray diffraction peaks. Thesolubility of each polymorph may vary, thus, identifying the existenceof pharmaceutical polymorphs is essential for providing pharmaceuticalswith predictable solubility profiles. It is desirable to investigate allsolid state forms of a drug, including all polymorphic forms, and todetermine the stability, dissolution and flow properties of eachpolymorphic form. Polymorphic forms of a compound can be distinguishedin a laboratory by X-ray diffraction spectroscopy and by other methodssuch as, infrared spectrometry. For a general review of polymorphs andthe pharmaceutical applications of polymorphs see G. M. Wall, PharmManuf. 3, 33 (1986); J. K. Haleblian and W. McCrone, J Pharm. Sci., 58,911 (1969); and J. K. Haleblian, J. Pharm. Sci., 64, 1269 (1975), all ofwhich are incorporated herein by reference.

As used herein, “breakthrough HE,” includes, for example, an increase ofthe Conn score to Grade ≧2 (e.g., 0 or 1 to ≧2) or a Conn and Asterixisscore increase of 1 grade each for those subjects that have a baselineConn score of 0.

As used herein, “time to the first breakthrough HE episode,” includes,for example, the duration between the date of first administration ofrifaximin and the date of first breakthrough HE episode.

As used herein, “time to first HE-related hospitalization,” includes,for example, the duration between the first dose of rifaximin and thedate of first HE-related hospitalization.

As used herein, “time to an increase from baseline in the Conn score”includes, for example, the duration between the first dose of rifaximinand the date of first increase in Conn score.

As used herein, “time to an increase from baseline in the asterixisgrade”, includes, for example, the duration between the first dose ofrifaximin and the date of first increase in asterixis grade.

As used herein, “mean change from baseline in the fatigue domain scoreof Chronic Liver Disease Questionnaire (CLDQ),at end of treatment (EOT)”is the mean score with a baseline from before the first administrationof rifaximin.

As used herein, “mean change from baseline in blood ammoniaconcentration at EOT,” includes the mean score with a baseline frombefore the first administration of rifaximin.

As used herein, the “time to diagnosis of spontaneous bacterialperitonitis (SBP),” includes, for example, the duration between thefirst dose of rifaximin and the date of first episode of SBP.

As used herein, the “mean change from baseline at each post-baseline incritical flicker frequency values,” is measured, for example, from abaseline established before the first administration of rifaximin.

“GI specific antibiotic,” and “GI antibiotic” as used herein includeantibiotic known to have an effect on GI disease. For example, arifamycin class antibiotic (e.g., rifaximin), neomycin, metronidazole,teicoplanin, ciprofloxacin, doxycycline, tetracycline, augmentin,cephalexin, penicillin, ampicillin, kanamycin, rifamycin, vancomycin,rifaximin, and combinations thereof are useful GI specific antibiotics.Even more preferable are GI specific antibiotics with low systemicabsorption, for example, rifaximin. Low systemic absorption includes,for example, less than 10% absorption, less than 5% absorption, lessthan 1% absorption and less than 0.5% absorption. Low systemicabsorption also includes, for example, from between about 0.01-1%absorption, from between about 0.05-1% absorption, from between about0.1-1% absorption, from between about 1-10% absorption, or from betweenabout 5-20% absorption.

As used herein, “subject” includes organisms which are capable ofsuffering from a bowel disorder or other disorder treatable by rifaximinor who could otherwise benefit from the administration of a rifaximin asdescribed herein, such as human and non-human animals. Preferred humananimals include human subjects. The term “non-human animals” of theinvention includes all vertebrates, e.g., mammals, e.g., rodents, e.g.,mice, and non-mammals, such as non-human primates, e.g., sheep, dog,cow, chickens, amphibians, reptiles, etc. Susceptible to a boweldisorder is meant to include subjects at risk of developing a boweldisorder infection, i.e., subjects suffering from immune suppression,subjects that have been exposed to other subjects with a bacterialinfection, physicians, nurses, subjects traveling to remote areas knownto harbor bacteria that causes travelers' diarrhea, etc.

The language “a prophylactically effective amount” of a compound refersto an amount of a compound of the invention of formula I, formula II, orotherwise described herein which is effective, upon single or multipledose administration to the subject, in preventing or treating hepaticencephalopathy.

Another embodiment includes articles of manufacture that comprise, forexample, a container holding a pharmaceutical composition suitable fororal administration of rifaximin in combination with printed labelinginstructions providing a discussion of when a particular dosage formextends remission of HE or prevents or delays future episodes of HE. Thedosage can be modified for administration to a subject suffering fromHE, or include labeling for administration to a subject suffering fromHE. Exemplary dosage forms and administration protocols are describedinfra. The composition will be contained in any suitable containercapable of holding and dispensing the dosage form and which will notsignificantly interact with the composition and will further be inphysical relation with the appropriate labeling. The labelinginstructions may be consistent with the methods of treatment asdescribed hereinbefore. The labeling may be associated with thecontainer by any means that maintain a physical proximity of the two, byway of non-limiting example, they may both be contained in a packagingmaterial such as a box or plastic shrink wrap or may be associated withthe instructions being bonded to the container such as with glue thatdoes not obscure the labeling instructions or other bonding or holdingmeans.

In one embodiment, the instructions will inform or advise a health careworker, prescribing physician, a pharmacist, or a subject that theyshould advise a patient suffering from hepatic encephalopathy thatadministration of rifaximin may induce cytochrome P450. In anotherembodiment, the instructions will inform the subject and/or thehealthcare provider that there is an extended time to remission orrelapse of subjects that take rifaximin. In another embodiment, theinstructions will inform the subject and/or the healthcare worker orprovider that rifaximin does not significantly alter the C_(max),AUC_(0-t), or AUC_(0-∞) of midazolam. In another embodiment, theinstructions will inform the subject and/or the healthcare worker orprovider that rifaximin does not increase the risk of QT prolongation.

Packaged compositions are also provided, and may comprise atherapeutically effective amount of rifaximin tablets or capsules. Kitsare also provided herein, for example, kits for treating HE in asubject. The kits may contain, for example, rifaximin and instructionsfor use when treating a subject for an HE. The instructions for use maycontain prescribing information, dosage information, storageinformation, and the like.

Kits may include pharmaceutical preparations of the GI specificantibiotics along with pharmaceutically acceptable solutions, carriersand excipients.

The α, β, γ, delta, epsilon and amorphous forms of rifaximin can beadvantageously used in the production of medicinal preparations havingantibiotic activity, containing rifaximin, for both oral and topicaluse. The medicinal preparations for oral use may contain rifaximin α orβ or γ together with other excipients, for example diluting agents suchas mannitol, lactose and sorbitol; binding agents such as starchs,gelatines, sugars, cellulose derivatives, natural gums andpolyvinylpyrrolidone; lubricating agents such as talc, stearates,hydrogenated vegetable oils, polyethylenglycol and colloidal silicondioxide; disintegrating agents such as starchs, celluloses, alginates,gums and reticulated polymers; coloring, flavoring and sweeteningagents.

Solid preparations of gastrointestinal specific antibioticsadministrable by the oral route include for instance coated and uncoatedtablets, soft and hard gelatin capsules, sugar-coated pills, lozenges,wafer sheets, pellets and powders in sealed packets.

Medicinal preparations may contain gastrointestinal specific antibioticstogether with usual excipients, such as white petrolatum, white wax,lanoline and derivatives thereof, stearylic alcohol, red iron oxide,propylene glycol, talc, sodium lauryl sulfate, ethers of fattypolyoxyethylene alcohols, disodium edentate, glycerol palmitostearate,esters of fatty polyoxyethylene acids, sorbitan monostearate, glycerylmonostearate, propylene glycol monostearate, hypromellose, polyethyleneglycols, sodium starch glycolate, methylcellulose, hydroxymethylpropylcellulose, sodium carboxymethylcellulose, microcrystallinecellulose, colloidal aluminium and magnesium silicate, titanium dioxide,propylene glycol, colloidal silicon dioxide, or sodium alginate.

West Haven Criteria (Conn Score):

Measurements of change in mental status may be done, for example, by theConn score (also known as the West Haven score). The Conn score has beenwidely used as a measure of mental state in HE studies and is based onthe criteria of Parsons-Smith as modified by Conn. Asterixis will not beconsidered when assessing the subject's status using the Conn scoringcriteria listed below.

The scale used in the Conn scoring system is provided below.

-   Grade 0=No personality or behavioral abnormality detected-   Grade 1=Trivial lack of awareness, euphoria or anxiety; shortened    attention span; impairment of addition or subtraction-   Grade 2=Lethargy; disorientation for time; obvious personality    change; inappropriate behavior-   Grade 3=Somnolence to semi-stupor, responsive to stimuli; confused;    gross disorientation; bizarre behavior-   Grade 4=Coma; unable to test mental state

EXAMPLES

It should be appreciated that embodiments of the invention should not beconstrued to be limited to the examples, which are now described;rather, the invention should be construed to include any and allapplications provided herein and all equivalent variations within theskill of the ordinary artisan.

Example 1

Subjects were instructed to take one tablet of 550 mg of rifaximin bymouth 2 times per day—approximately every 12 hours. The rifaximin may beco-administered with other medications, for example, lactulose,antidepressants, anti-inflammatory, methadone, prescription andnon-prescription sleep aids (e.g., Lunesta™ (eszopiclone) and Ambien®(zolpidem tartrate)), and antihistamines, diuretics, laxatives or stoolsofteners, neurontin (gabapentin) and lyrica (pregabalin).

Lactulose use was optional for subjects. For subjects who usedlactulose, it was titrated to a dose during the 3 to 7-day observationperiod according to accepted medical practice.

Asterixis Grade

Asterixis (flapping tremor) was determined with the subject holding botharms and forearms extended with wrists dorsiflexed and fingers open for≧30 seconds. Asterixis was measured on a continuum of 5 grades, e.g.,grades 0 and 4=no abnormal movement vs. almost continuous flappingmotions, respectively as shown below:

Grade 0=No tremors;Grade 1=Rare flapping motions;Grade 2=Occasional, irregular flaps;Grade 3=Frequent flaps; andGrade 4=Almost continuous flapping motions.

Efficacy in regard to asterixis grade was measured as time to anyincrease from baseline in asterixis grade. Time to an increase inasterixis grade was computed as the number of days from the first doseof rifaximin to the initial occurrence of an increase from baseline inasterixis grade.

Breakthrough HE Episode

Relative risk of experiencing a breakthrough HE episode (e.g., Connscore Grade ≧2, (e.g., 0 or 1 to ≧2) or a Conn and asterixis scoreincrease of 1 grade each) for each subject in the trial taking eitherrifaximin or the placebo was measured. The analysis compared time tofirst breakthrough HE episode for rifaximin versus placebo usingsurvival analysis methods. Time to first breakthrough HE episode wascomputed as the number of days from the first dose of rifaximin to theinitial occurrence of breakthrough HE (e.g., Conn score Grade ≧2, or aConn and asterixis score increase of 1 grade each).

Change in mental status was measured by the Conn score (also known asthe West Haven score). The Conn score has been widely used as a measureof mental state in HE studies and is based on the criteria ofParsons-Smith as modified by Conn. The scale used in the Conn scoringsystem is described above.

Subjects had a Conn score of 0 or 1. An increase in the Conn score ofgreater than or equal to grade 2 was considered as a breakthrough HEepisode.

Hepatic Encephalopathy Scoring Algorithm (HESA)

The Hepatic Encephalopathy Scoring Algorithm (HESA) is a method thatuses both clinical and neuropsychological assessments to assess mentalstatus. The Algorithm has been validated previously and has beencorrelated with the Conn criteria.

Critical Flicker Frequency scores

The critical flicker frequency (CFF) was assessed for each subject usinga specialized CFF instrument. The CFF is the frequency at which thesubject observes a constant light transition to a flickering light andis measured in Hertz (Hz). CFF is an objective assessment of mentalstatus. A CFF value of 39 Hz has been shown to be the threshold forseparation between subjects who have manifest HE (e.g., Conn ≧1) andthose without HE symptoms (e.g., Conn=0), with a lower CFF valueindicating more severe HE⁽⁴³⁾.

The CFF was measured on a continuous scale and was the mean of 8separate fusion-to-flicker transition tests performed in rapidsuccession.

Ammonia Concentrations

Venous blood samples (10 mL) were collected and ammonia concentrationswere obtained by methods known in the art.

Time to Increase from Baseline in Either the Conn Score (Mental StateGrade) or Asterixis Grade

To analyze the time to a first breakthrough HE episode, survivalanalysis methods were used to assess the effectiveness of the rifaximintreatment on the time to increase from baseline in either the Conn score(mental state grade) or asterixis grade. Time to increase in either theConn score or asterixis grade was computed as the number of days fromthe first dose of rifaximin to the initial occurrence of either anincrease from baseline in Conn score or asterixis grade. The analysis oftime to increase in either Conn score or asterixis grade were based onthe comparison of time to event between rifaximin and placebo.

Time to First HE-Related Hospitalization

The effect of rifaximin on time to first HE-related hospitalization wasdetermined. Time to first HE-related hospitalization was computed as thenumber of days from the first dose of rifaximin to the firsthospitalization for an HE related event. The analysis of time to firstHE-related hospitalization was based on the comparison of time tohospitalization between rifaximin and placebo.

Time to Development of Spontaneous Bacterial Peritonitis

The effect of rifaximin on time to development of spontaneous bacterialperitonitis (SBP) was determined. Time to development of SBP wascomputed as the number of days from the first dose of rifaximin to thetime of peritoneal fluid collection that resulted in a positive test forSBP. The analysis of time to development of SBP was based on thecomparison of time to event between rifaximin and placebo.

Mean Change from Baseline in Blood Ammonia Concentration and CriticalFlicker Frequency Values Over Time

Mean values and mean changes from baseline in blood ammoniaconcentration and critical flicker frequency values were collected.Analyses of blood ammonia concentrations and critical flicker frequencyvalues were based upon quantitative values (not qualitative grades).Treatment differences for mean change from baseline in these parameterswas estimated using a mixed effects model with fixed effects for timeand baseline value.

Mean Daily Lactulose Consumption Over Time

A subject's daily lactulose consumption was used to compute mean dailylactulose consumption for each month. Treatment differences for meanchange from baseline in mean daily lactulose consumption were estimated.

CLDQ

The CLDQ includes 29 items in the following six domains: abdominalsymptoms (three items), fatigue (five items), systemic symptoms (fiveitems), activity (three items), emotional function (eight items), andworry (five items). Summary scores for the CLDQ overall and each of thesix domains were computed and summarized at baseline and Days 28, 56,84, 112, 140 and 168 using descriptive statistics. Treatment differencesfor mean change in overall score and domain scores from baseline to Days28, 56, 84, 112, 140 and 168 were collected summarized and comparedbetween treatments.

Treatment differences for mean change from baseline to EOT weredetermined as the change from baseline at EOT in fatigue domain score ofChronic Liver Disease Questionnaire (CLDQ). Similarly, the mean changefrom baseline in blood ammonia concentration at EOT was also determined.

Assessment of Quality of Life

The SF-36, Chronic Liver Disease Questionnaire (CLDQ), and EpworthSleepiness Scale were used to measure health related quality of life.The 29 item CLDQ questionnaire consists of the following domains:fatigue, activity, emotional function, abdominal symptoms, systemicsymptoms, and worry.

Epworth Sleepiness Scale

Total scores for the Epworth Sleepiness Scale were computed andsummarized at baseline and Days 28, 56, 84, 112, 140 and 168 usingdescriptive statistics. Treatment differences for mean change in totalscores from baseline to Days 28, 56, 84, 112, 140 and 168 weresummarized and compared between treatments.

FIG. 1 is a line graph showing Lactulose daily use between subjectstaking placebos and subjects taking rifaximin as described above.

FIG. 2 is a line graph showing Kaplan Meier estimates of thedistribution of time to a breakthrough HE event for the placebo groupand the rifaximin group. As indicated there was an increased time tobreakthrough HE events for subjects taking rifaximin in comparison tosubjects taking the placebo.

FIG. 3 is a line graph showing Kaplan Meier estimates of thedistribution of time to a first HE related hospitalization. As indicatedthere was an increased time to hospitalization for subjects takingrifaximin in comparison to the placebo group.

FIG. 4 is a line graph showing Kaplan Meier estimates of thedistribution of time to a first increase in Conn scores. As indicatedthere was an increased time to the first increase in Conn scores forsubjects taking rifaximin in comparison to the placebo group.

FIG. 5 is a line graph showing Kaplan Meier estimates of thedistribution of time to a first increase in Asterixis grade. Asindicated there was an increased time to the first increase in Asterixisgrade for subjects taking rifaximin in comparison to the placebo group.

Example 2

The following tables provide further evidence supporting theadvantageous use of GI specific antibiotics, such as rifaximin, to treatsubjects suffering from HE.

TABLE 1 Time to Onset of Breakthrough HE Episode Placebo (N = 159) 550mg Rifaximin BID (N = 140) Cumulative Conditional Cumulative ConditionalAt Occurrences Occurrences Probability of At Occurrences OccurrencesProbability of Days Risk of Events of Events Events (SE) Survival Riskof Events of Events Events (SE) Survival  [0-28) 158 20 20 0.13 (0.03)1.0000 140 13 13 0.09 (0.02) 1.0000 [28-56) 137 23 43 0.17 (0.03) 0.8734126 4 17 0.03 (0.02) 0.9071 [56-84) 113 14 57 0.12 (0.03) 0.7262 120 623 0.05 (0.02) 0.8783  [84-140) 98 10 67 0.10 (0.03) 0.6363 112 7 300.06 (0.02) 0.8344 [140-168) 84 6 73 0.07 (0.03) 0.5713 98 1 31 0.01(0.01) 0.7820 >=168 38 0 73 0.00 (0.00) 0.5305 46 0 31 0.00 (0.00)0.7740 Harzard Ratio: 0.421 95% CI: (0.276, 0.641) p-value: <.0001

TABLE 2 Time to Onset of Breakthrough HE Episode by Baseline Conn ScoreLevel Placebo (N = 107) 550 mg Rifaximin BID (N = 93) CumulativeConditional Cumulative Conditional At Occurrences OccurrencesProbability of At Occurrences Occurrences Probability of Days Risk ofEvents of Events Events (SE) Survival Risk of Events of Events Events(SE) Survival  [0-28) 107 13 13 0.12 (0.03) 1.0000 93 11 11 0.12 (0.03)1.0000 [28-56) 93 16 29 0.17 (0.04) 0.8779 81 3 14 0.04 (0.02) 0.8817[56-84) 77 7 36 0.09 (0.03) 0.7269 77 1 15 0.01 (0.01) 0.8491  [84-140)69 5 41 0.07 (0.03) 0.6608 75 3 18 0.04 (0.02) 0.8380 [140-168) 61 4 450.07 (0.03) 0.6129 68 1 19 0.01 (0.01) 0.8042 >=168 27 0 45 0.00 (0.00)0.5724 32 0 19 0.00 (0.00) 0.7924 Harzard Ratio: 0.441 95% CI: (0.258,0.754) p-value: 0.0028

TABLE 3 Time to Onset of Breakthrough HE Episode by Prior Lactulose UsePlacebo (N = 142) 550 mg Rifaximin BID (N = 123) Cumulative ConditionalCumulative Conditional At Occurrences Occurrences Probability of AtOccurrences Occurrences Probability of Days Risk of Events of EventsEvents (SE) Survival Risk of Events of Events Events (SE) Survival [0-28) 141 19 19 0.13 (0.03) 1.0000 123 12 12 0.10 (0.03) 1.0000[28-56) 121 21 40 0.17 (0.03) 0.8652 110 4 16 0.04 (0.02) 0.9024 [56-84)100 13 53 0.13 (0.03) 0.7151 104 5 21 0.05 (0.02) 0.8696  [84-140) 86 1063 0.12 (0.03) 0.6221 97 7 28 0.07 (0.03) 0.8278 [140-168) 73 5 68 0.07(0.03) 0.5498 84 1 29 0.01 (0.01) 0.7678 >=168 33 0 68 0.00 (0.00)0.5121 39 0 29 0.00 (0.00) 0.7586 Harzard Ratio: 0.424 95% CI: (0.274,0.655) p-value: 0.0001

TABLE 4 Time to Onset of First HE-Related Hospitalization Placebo (N =159) 550 mg Rifaximin BID (N = 140) Cumulative Conditional CumulativeConditional At Occurences Occurrences Probability of At OccurencesOccurrences Probability of Days Risk of Events of Events Events (SE)Survival Risk of Events of Events Events (SE) Survival  [0-28) 154 11 110.07 (0.02) 1.0000 138 6 6 0.04 (0.02) 1.0000 [28-56) 131 14 25 0.11(0.03) 0.9286 125 4 10 0.03 (0.02) 0.9564 [56-84) 105 7 32 0.07 (0.02)0.8293 113 5 15 0.04 (0.02) 0.9258  [84-140) 85 8 40 0.09 (0.03) 0.7743100 5 20 0.05 (0.02) 0.8848 [140-168) 65 2 42 0.03 (0.02) 0.7023 86 3 230.04 (0.02) 0.8403 >=168 30 0 42 0.00 (0.00) 0.6810 39 0 23 0.00 (0.00)0.8108 Harzard Ratio: 0.521 95% CI: (0.313, 0.858) p-value: 0.0107

TABLE 5 Time to Any Increase from Baseline in Conn Score Placebo (N =159) 550 mg Rifaximin BID (N = 140) Cumulative Conditional CumulativeConditional At Occurrences Occurrences Probability of At OccurrencesOccurrences Probability of Days Risk of Events of Events Events (SE)Survival Risk of Events of Events Events (SE) Survival  [0-28) 156 26 260.17 (0.03) 1.0000 139 17 17 0.12 (0.03) 1.0000 [28-56) 125 21 47 0.17(0.03) 0.8333 119 5 22 0.04 (0.02) 0.8777 [56-84) 100 15 62 0.15 (0.04)0.6928 109 9 31 0.08 (0.03) 0.8407  [84-140) 80 10 72 0.13 (0.04) 0.588394 5 36 0.05 (0.02) 0.7713 [140-168) 62 5 77 0.08 (0.03) 0.5143 79 0 360.00 (0.00) 0.7302 >=168 27 0 77 0.00 (0.00) 0.4729 37 1 37 0.03 (0.03)0.7302 Harzard Ratio: 0.463 95% CI: (0.312, 0.685) p-value: <.0001

TABLE 6 Time to Onset of Breakthrough HE Episode by Baseline MELD ScoreLevel Placebo (N = 44) 550 mg Rifaximin BID (N = 34) CumulativeConditional Cumulative Conditional At Occurrences OccurrencesProbability of At Occurrences Occurrences Probability of Days Risk ofEvents of Events Events (SE) Survival Risk of Events of Events Events(SE) Survival  [0-28) 44 2 2 0.05 (0.03) 1.0000 34 1 1 0.03 (0.03)1.0000 [28-56) 42 4 6 0.10 (0.05) 0.9545 33 0 1 0.00 (0.00) 0.9706[56-84) 38 1 7 0.03 (0.03) 0.8636 32 0 1 0.00 (0.00) 0.9706  [84-140) 373 10 0.08 (0.04) 0.8409 32 1 2 0.03 (0.03) 0.9706 [140-168) 33 4 14 0.12(0.06) 0.7727 28 0 2 0.00 (0.00) 0.9398 >=168 14 0 14 0.00 (0.00) 0.679113 0 2 0.00 (0.00) 0.9398 Harzard Ratio: 0.171 95% CI: (0.039, 0.754)p-value: 0.0197

TABLE 7 Time to Onset of Breakthrough HE Episode by Baseline MELD ScoreLevel Placebo (N = 86) 550 mg Rifaximin BID (N = 85) CumulativeConditional Cumulative Conditional At Occurrences OccurrencesProbability of At Occurrences Occurrences Probability of Days Risk ofEvents of Events Events (SE) Survival Risk of Events of Events Events(SE) Survival  [0-28) 86 15 15 0.18 (0.04) 1.0000 85 8 8 0.09 (0.03)1.0000 [28-56) 70 13 28 0.19 (0.05) 0.8246 77 2 10 0.03 (0.02) 0.9059[56-84) 56 11 39 0.20 (0.05) 0.6703 73 3 13 0.04 (0.02) 0.8822  [84-140)45 7 46 0.16 (0.05) 0.5387 68 6 19 0.09 (0.03) 0.8459 [140-168) 36 2 480.06 (0.04) 0.4539 58 1 20 0.02 (0.02) 0.7713 >=168 16 0 48 0.00 (0.00)0.4284 27 0 20 0.00 (0.00) 0.7580 Harzard Ratio: 0.329 95% CI: (0.195,0.556) p-value: <.0001

TABLE 8 Time to Onset of Breakthrough HE Episode by Baseline MELD ScoreLevel Placebo (N = 14) 550 mg Rifaximin BID (N = 11) CumulativeConditional Cumulative Conditional At Occurrences OccurrencesProbability of At Occurrences Occurrences Probability of Days Risk ofEvents of Events Events (SE) Survival Risk of Events of Events Events(SE) Survival  [0-28) 14 3 3 0.21 (0.11) 1.0000 11 1 1 0.09 (0.09)1.0000 [28-56) 11 4 7 0.36 (0.15) 0.7857 10 0 1 0.00 (0.00) 0.9091[56-84) 7 2 9 0.29 (0.17) 0.5000 10 3 4 0.30 (0.14) 0.9091  [84-140) 5 09 0.00 (0.00) 0.3571 7 0 4 0.00 (0.00) 0.6364 [140-168) 4 0 9 0.00(0.00) 0.3571 7 0 4 0.00 (0.00) 0.6364 >=168 2 0 9 0.00 (0.00) 0.3571 30 4 0.00 (0.00) 0.6364 Harzard Ratio: 0.403 95% CI: (0.123, 1.313)p-value: 0.1315

TABLE 9 Time to Onset of Breakthrough HE Episode by Prior Lactulose UsePlacebo (N = 134) 550 mg Rifaximin BID (N = 127) Cumulative ConditionalCumulative Conditional At Occurrences Occurrences Probability of AtOccurrences Occurrences Probability of Days Risk of Events of EventsEvents (SE) Survival Risk of Events of Events Events (SE) Survival [0-28) 134 18 18 0.13 (0.03) 1.0000 127 12 12 0.09 (0.03) 1.0000[28-56) 115 20 38 0.17 (0.04) 0.8652 114 4 16 0.04 (0.02) 0.9055 [56-84)95 14 52 0.15 (0.04) 0.7147 108 6 22 0.06 (0.02) 0.8737  [84-140) 80 961 0.11 (0.04) 0.6094 100 6 28 0.06 (0.02) 0.8252 [140-168) 68 5 66 0.07(0.03) 0.5408 88 1 29 0.01 (0.01) 0.7754 >=168 31 0 66 0.00 (0.00)0.5011 41 0 29 0.00 (0.00) 0.7666 Harzard Ratio: 0.399 95% CI: (0.258,0.618) p-value: <.0001

TABLE 10 Time to Any Increase from Baseline in Asterixis Grade Placebo(N = 159) 550 mg Rifaximin BID (N = 140) Cumulative ConditionalCumulative Conditional At Occurrences Occurrences Probability of AtOccurrences Occurrences Probability of Days Risk of Events of EventsEvents (SE) Survival Risk of Events of Events Events (SE) Survival [0-28) 154 20 20 0.13 (0.03) 1.0000 137 13 13 0.10 (0.03) 1.0000[28-56) 120 15 35 0.13 (0.03) 0.8697 116 7 20 0.06 (0.02) 0.9048 [56-84)91 4 39 0.04 (0.02) 0.7610 101 7 27 0.07 (0.03) 0.8499  [84-140) 76 6 450.08 (0.03) 0.7275 87 3 30 0.03 (0.02) 0.7910 [140-168) 61 4 49 0.07(0.03) 0.6701 74 1 31 0.01 (0.01) 0.7637 >=168 27 1 50 0.04 (0.04)0.6262 34 1 32 0.03 (0.03) 0.7534 Harzard Ratio: 0.646 95% CI: (0.414,1.008) p-value: 0.0523

TABLE 11 Mean Change from Baseline in Blood Ammonia Concentration(μg/dL) 550 mg Rifaximin Placebo BID Assessment Time (N = 159) (N = 140)P-value Day 28 n 126 121 Mean 89.3 88.4 SD 48.19 49.02 Median 87.0 74.0Min 2 25 Max 315 326 Change from Baseline to Day 28 n 117 117 0.6268Mean −1.1 −2.1 SD 48.32 44.37 Median 1.0 −2.0 Min −252 −164 Max 133 176

TABLE 12 Mean Change from Baseline in Critical Flicker Frequency Test(Hz) 550 mg Rifaximin Placebo BID Assessment Time (N = 159) (N = 140)P-value Day 140 n 70 87 Mean 38.7 38.7 SD 5.47 4.76 Median 38.8 38.9 Min26 27 Max 50 49 Change from Baseline to Day 140 n 70 87 0.0266 Mean 1.11.4 SD 4.10 4.84 Median 0.9 1.5 Min −12 −15 Max 12 12

TABLE 13 Mean Change from Baseline in Critical Flicker Frequency Test(Hz) 550 mg Rifaximin Placebo BID Assessment Time (N = 159) (N = 140)P-value EOT n 155 139 Mean 37.6 37.8 SD 5.98 4.88 Median 37.9 37.8 Min21 25 Max 50 49 Change from Baseline to EOT n 155 139 0.0320 Mean 0.40.9 SD 4.70 4.75 Median 0.2 0.1 Min −12 −14 Max 16 11

TABLE 14 Number of Subjects in Each Level of Change from Baseline inConn Score by Treatment Group 550 mg Odds Ratio Rifaximin (550 mgAssessment Placebo BID Rifaximin 95% CI for P- Time Statistics (N = 159)(N = 140) BID/Placebo) Odds Ratio value Change from Baseline to EOT −1 n(%) 18 (11.5%) 26 (18.7%) 2.46 (1.49, 4.09) 0.0005 0 n (%) 100 (63.7%)101 (72.7%) 1 n (%) 29 (18.5%) 10 (7.2%) 2 n (%) 9 (5.7%) 2 (1.4%) 3 n(%) 1 (0.6%) 0 n 157 139 Mean 0.2 −0.1 SD 0.74 0.56 Median 0.0 0.0 Min−1 −1 Max 3 2

TABLE 15 Number of Subjects in Each Level of Change from Baseline inAsterixis Grade by Treatment Group 550 mg Odds Ratio Rifaximin (550 mgAssessment Placebo BID Rifaximin 95% CI for P- Time Statistics (N = 159)(N = 140) BID/Placebo) Odds Ratio value Change from Baseline to EOT −2 n(%) 1 (0.6%) 1 (0.7%) 1.88 (1.10, 3.23) 0.0207 −1 n (%) 14 (8.9%) 18(12.9%) 0 n (%) 114 (72.6%) 108 (77.7%) 1 n (%) 18 (11.5%) 10 (7.2%) 2 n(%) 8 (5.1%) 2 (1.4%) 3 n (%) 1 (0.6%) 0 4 n (%) 1 (0.6%) 0 n 157 139Mean 0.2 0.0 SD 0.76 0.54 Median 0.0 0.0 Min −2 −2 Max 4 2

TABLE 16 Mean Change from Baseline for Epworth Sleepiness Total Score550 mg Rifaximin Placebo BID Assessment Time (N = 159) (N = 140) P-valueDay 28 N 91 87 Mean 9.1 10.0 SD 4.84 5.51 Median 8.0 9.0 Min 0 0 Max 2123 Change from Baseline to Day 28 N 90 86 0.0593 Mean −1.1 −0.2 SD 4.793.53 Median −1.0 0.0 Min −17 −14 Max 14 7

TABLE 17 Time to Onset of First HE-Related Hospitalization Placebo (N =159) 550 mg Rifaximin BID (N = 140) Cumulative Conditional CumulativeConditional At Occurrences Occurrences Probability of At OccurrencesOccurrences Probability of Days Risk of Events of Events Events (SE)Survival Risk of Events of Events Events (SE) Survival  [0-28) 155 11 110.07 (0.02) 1.0000 139 4 4 0.03 (0.01) 1.0000 [28-56) 132 12 23 0.09(0.03) 0.9288 130 4 8 0.03 (0.02) 0.9711 [56-84) 108 7 30 0.06 (0.02)0.8440 119 4 12 0.03 (0.02) 0.9411  [84-140) 88 4 34 0.05 (0.02) 0.7893106 5 17 0.05 (0.02) 0.9094 [140-168) 72 2 36 0.03 (0.02) 0.7535 92 2 190.02 (0.02) 0.8665 >=168 34 0 36 0.00 (0.00) 0.7325 43 0 19 0.00 (0.00)0.8475 Harzard Ratio: 0.500 95% CI: (0.287, 0.873) p-value: 0.0129

Example 3

Induction of CYP3A4 by rifaximin was observed based on decreasedmidazolam AUC by ˜25%. A higher systemic exposure is expected in amajority of the target patient population.

When rifaximin was orally administered at high doses (1650 mg/day) forat least 7 days, the mean C_(max), AUC_(0-t), and AUC_(0-∞) of midazolamwere reduced by <25%. Rifaximin is a potential CYP3A4 inducer, in vitrostudies have shown it to have a lower induction potency than rifampin.(The estimated intestinal lumen concentration of rifaximin isapproximately 5 μM. In the in vitro study, CYP3A4 activity was induced1.7-fold and 1.8-fold at rifaximin 1 μM and 10 μM; at the sameconcentrations, rifampin induced CYP3A4 3.7-fold and 4-fold,respectively. Furthermore, rifaximin's gut-targeted distribution isbelieved to limit its CYP3A4 induction mechanism to the intestine,sparing hepatic induction as a result of low systemic exposure. That is,there is a separation of intestinal and hepatic induction for rifaximinThis is shown in studies disclosed herein in humans receiving rifaximin,as supported by the absence of induction when either intravenous or oralmidazolam was administered following rifaximin 200 mg TID for up to 7.

Without wishing to be bound by any particular scientific theory, it isthought that any risk of hepatic CYP3A4 induction likely is furthermitigated in hepatically impaired patients, for whom significantfractions of portal blood flow are shunted around the liver;³ therefore,their increased systemic exposure should be accompanied by aproportional decrease in exposure to hepatocytes and the patients shouldincur no net increase in risk of hepatic CYP3A4 induction.

Example 4

Two clinical drug-drug interaction studies were conducted with therifaximin 200 mg tablet and one drug-drug interaction study with the 550mg tablet. Two studies using midazolam, a known substrate for CYP3A4,and 1 study using an oral contraceptive containing ethinyl estradiol andnorgestimate were conducted to assess the effect of rifaximin on thepharmacokinetics of these drugs. Based on the results of these studiesand in vitro induction and inhibition studies using human liverfractions, no clinically relevant drug interactions are anticipated withXIFAXAN.

Although in vitro studies demonstrated the potential of rifaximin tointeract with cytochrome P450 3A4 (CYP3A4), a clinical drug-druginteraction study demonstrated that rifaximin did not significantlyaffect the pharmacokinetics of midazolam either presystemically orsystemically. An additional clinical drug-drug interaction study showedno effect of rifaximin on the presystemic metabolism of an oralcontraceptive containing ethinyl estradiol and norgestimate. Therefore,clinical interactions with drugs metabolized by human cytochrome P450isoenzymes are not expected.

Two studies have been performed to evaluate the potential for druginteractions with midazolam. The first was an open-label, randomized,crossover, drug-interaction trial designed to assess the effect ofrifaximin 200 mg administered orally (PO) every 8 hours (Q8H) for 3 daysand every 8 hours for 7 days, on the pharmacokinetics of a single doseof either midazolam 2 mg intravenous (IV) or midazolam 6 mg PO. Nosignificant difference was observed in the metrics of systemic exposureor elimination of IV or PO midazolam or its major metabolite,1′-hydroxymidazolam, between midazolam alone or together with rifaximin.Therefore, rifaximin was not shown to significantly affect intestinal orhepatic CYP3A4 activity.

The second study, an open-label, drug-interaction study examined theeffect of rifaximin, 550 mg three times daily, on orally administered(PO) midazolam 2 mg when dosed for 7 and 14 consecutive days. In thisstudy rifaximin was shown to be a weak inducer of CYP3A4; given the lowsystemic exposure of rifaximin, this interaction is believed to belimited to the gastrointestinal tract. This induction is both dose- anddosing-duration dependent. When rifaximin was orally administered athigh doses (1650 mg/day) for at least 7 days, the mean C_(max),AUC_(0-t), and AUC_(0-∞) of midazolam were reduced by <25%.

In vitro hERG potency and in vitro protein binding of rifaximin. In thein vitro hERG studies, rifaximin concentrations up to 300 μM failed toachieve 50% inhibition of the hERG potassium current. Due to rifaximinprecipitation at 300 μM, the IC₅₀ was estimated to be greater than 100μM. In fact, 50% inhibition could not be achieved; at 100 μM, meaninhibition was 34.5%. The highest C_(max) observed in a hepaticallyimpaired patient in a study was 52.2 ng/mL (0.0664 μM); the highest freefraction observed in a subset of plasma samples from patients enrolledin this study was 44.7%. Using these numbers, the highest anticipatedfree plasma exposure would be 0.03 μM, which represents a reduction of≧3000-fold in comparison with the highest concentration at whichrifaximin could be tested in the hERG experiments. This safety margingreatly exceeds the 30-fold separation between hERG IC₅₀ and unboundC_(max) that is commonly associated with minimization of risk ofclinical QT prolongation.⁴

Example 5

An efficacy parameter for a first study was the occurrence of an episodeof breakthrough overt HE during treatment. Breakthrough overt HEepisodes were measured by using the Conn score (or West Haven grade),and the asterixis grade. A breakthrough overt HE episode, as defined forthe first study, was a marked, clinically significant deterioration inneurological function that can result in a deleterious effect on selfcare, and lead to hospitalization. The efficacy endpoint, time to firstbreakthrough overt HE episode, showed a highly significant protectiveeffect of rifaximin (p<0.0001 for between-group difference in relativerisk). Rifaximin treatment resulted in a 57.9% reduction, when comparedwith placebo, in the risk of experiencing breakthrough overt HE duringthe 6-month treatment period.

In addition, this study also showed that the time to first breakthroughovert HE also showed a highly significant protective effect of rifaximinwhen analyzed in separate geographic regions, North America versusRussia.

Rifaximin treatment results in fewer overt HE episodes that mayotherwise incapacitate the patient, may alleviate the burden on familymembers who are required to care for the patient, and reduces the burdenof hospitalization in this patient population and the healthcare system.

In a second study, similar results were shown, for example, the secondstudy with respect to time to first breakthrough overt HE episode: theKaplan-Meier estimates of time to first breakthrough overt HE episodewere similar between the rifaximin group in the first study and newrifaximin subjects in this second study. Also, similar proportions ofsubjects had breakthrough overt HE in the rifaximin group of the firststudy (22%, 31 of 140 [rifaximin group]) and in the new rifaximin groupof the second study (27.6%, 54 of 196).

Additionally, when the first study placebo subjects crossed over torifaximin therapy by entering the second study, a protective effect ofrifaximin was observed: the first study a 70% reduction in risk ofexperiencing breakthrough overt HE during rifaximin treatment in thesecond study when compared with their prior placebo experience in thefirst study. This reduction took place in spite of the aging andpresumably progressing nature of the population with chronic liverdisease.

The second study also showed that the protective effect of rifaximin wasdurable: the estimate of time-to-first breakthrough HE demonstratedlong-term maintenance of remission from breakthrough HE when rifaximinsubjects in remission after participation in the first study werefollowed in the second study (up to 680 days of rifaximin therapy;median exposure durations were 168 days in the first study and 253 daysin the second study). The incidence of breakthrough HE episode for theserifaximin subjects relative to the first study placebo was lower, anindication of fewer breakthrough HE episodes with rifaximin treatment.

A critical flicker frequency (CFF) assessment, a recognized quantitativemeasure of CNS dysfunction, was an efficacy endpoint in the first study.CFF tests utilize the correlation between cerebral processing ofoscillatory visual stimuli and CNS impairment due to increased HEseverity.^(10,11,12,13) This test identifies a frequency at which aflickering light is perceived as steady. A decline in this frequency hasbeen associated with increasing severity of HE. Likewise, elevation inblood ammonia, another endpoint in the first study, is a quantitativeassessment associated with the CNS effects underlying overt HE.

Comparisons of changes from baseline to end of study in CFF results andin venous ammonia levels showed statistically significant, greaterimprovement over the course of the study in the rifaximin group whencompared to placebo (p=0.0320 for CFF changes and p=0.0391 for venousammonia changes). In the first study, a correlation between CFF resultsand breakthrough overt HE (primary efficacy measure) was noted. Venousammonia levels were found to be correlated to the occurrence ofbreakthrough overt HE in the first study.

Results for other efficacy endpoints also demonstrated protectiveeffects of rifaximin. In particular, the other efficacy endpoint of timeto first HE-related hospitalization showed a reduction in risk forrifaximin subjects.

In the first study, the analysis of time to first HE-relatedhospitalization (e.g., hospitalization directly resulting from HE orhospitalization complicated by HE) demonstrated that the reduction inrisk of hospitalization due to HE was 50% in the rifaximin group, whencompared with placebo, during the 6-month treatment period. TheHE-related hospitalization rate was 0.38 event/person exposure years(PEY), rifaximin versus 0.78 event/PEY, placebo after normalization toexposure.

In the first study, the risk of HE-caused hospitalization (e.g.,hospitalization directly resulting from HE only) was reduced by 56% inthe rifaximin group when compared with placebo. The HE-causedhospitalization rate was 0.30 events/PEY in the rifaximin group versus0.72 event/PEY in the placebo group.

In the first study, the risk of all-cause hospitalization rate wasreduced by 30% in the rifaximin group when compared to placebo. Theall-cause hospitalization rate was 0.92 events/PEY in the rifaximingroup versus 1.31 event/PEY in the placebo group.

In the second study, the low HE-caused hospitalization rate wasmaintained at rates consistent with those in the first study: HE-causedhospitalization rate was 0.29 event/PEY and all cause hospitalization inthe second study was 0.66 event/PEY. The consistently lowHE-related/HE-caused hospitalization rate in rifaximin-treated subjectsin the first study and in the second study was at least partly a resultof maintaining remission from demonstrated HE in subjects with end-stageliver disease.

Hepatic encephalopathy is associated with a low quality of life comparedto age-matched patients without HE. Patients with HE experience symptomsincluding fatigue, daytime sleepiness, and lack of awareness (Conn score1); and confusion and disorientation (Conn score 2) that significantlyinterfere with day-to-day function and decreased ability for self care.Often, this lack of self care can lead to improper nutrition andnon-adherence to therapy and can further escalate into more severesymptoms such as increased somnolence, gross disorientation and stupor,which require hospitalization. Rifaximin treatment protects against HErelated/caused hospitalization, thereby improving the functional statusfor the patient and benefiting his/her caregiver; and reducing theeconomic cost related to liver cirrhosis and associated HE.

There are limited treatment options in the United States for patientswith recurrent HE. Neomycin sulfate is only approved for the adjunctivetherapy in hepatic coma. Conventional therapy aims to lower theproduction and absorption of ammonia. Nonabsorbable disaccharides, eg,lactulose or lactitol, are typically used as first-line therapy for HE.There is evidence that nonabsorbable disaccharides lower plasma levelsof ammonia by changing nitrogen metabolism in colonic flora andincreasing fecal excretion of nitrogen. Broadspectrum, GI-activeantibiotics including neomycin, metronidazole, vancomycin, andparomomycin have been used with or without lactulose. These antibioticsappear to act indirectly by inhibiting the splitting of urea bydeaminating bacteria, thus reducing the production of ammonia and otherpotential toxins. Current guidelines recommend (not FDA approved)antibiotic therapy with neomycin or metronidazole as an alternative totreatment with nonabsorbable disaccharides.

Common side effects of nonabsorbable disaccharide (e.g., lactulose)therapy include an unpleasant taste that can hinder treatmentcompliance, a dosing schedule that is linked to bowel habits, and GIside effects such as bloating, abdominal cramps, and diarrhea. Diarrhearesulting in dehydration has been reported with the use of lactulose, asignificant consequence for patients with HE as electrolyteabnormalities can worsen HE and lead to renal dysfunction.

The use of systemically absorbed antibiotics such as neomycin in thetreatment of HE is hampered by ototoxicity and nephrotoxicity associatedwith long-term use. The incidence of aminoglycoside-inducednephrotoxicity is substantially greater in patients with advanced liverdisease than in patients without liver disease. The frequency ofaminoglycoside-induced nephrotoxicity in the general population is 3% to11%. Leitman reported that nephrotoxicity occurred in 73% of patientswith liver disease versus 34% of patients without liver disease whoreceived aminoglycosides by intravenous administration duringhospitalization; and Cabrera reported that renal tubular damage orfunctional renal impairment was observed in 60% ofaminoglycoside-treated cirrhotic patients (intravenous administrationduring hospitalization). Additionally, a high mortality rate andsustained renal damage were noted in cirrhotic patients who developedaminoglycoside-induced renal tubular damage. Therefore, aminoglycosidesare now widely considered as contraindicated in patients with advancedliver disease.

Rifaximin is an attractive therapy for the treatment of patients with HEbecause of its demonstrated effectiveness, favorable safety profile, andbecause of disadvantages of systemic aminoglycosides and nonabsorbabledisaccharides. Rifaximin has a broad spectrum of in vitro antibacterialactivity against both Gram-positive and Gram-negative bacteria andagainst aerobic and anaerobic isolates.

Since rifaximin is poorly absorbed after oral administration, the drugis selectively active in the gastrointestinal tract. Additionally, thereis a low risk of drug-drug interactions with the use of rifaximin.Rifaximin has a lower rate of fecal eradication of pathogens comparedwith other commonly used antibacterial drugs and causes minimalalterations in gut flora suggesting that rifaximin has a differentmechanism of action than other commonly used drugs in enteric bacterialinfection, such as the fluoroquinolones. The risk of the development ofantibiotic resistance is low during chronic treatment with rifaximinwhen compared to other systemic antibiotics such as neomycin, possiblybecause resistance is mediated by a mutation in host cell DNA and is notplasmid based.

In a retrospective chart review, the numbers and durations ofhospitalizations due to HE, the total cost of therapy, and HE endpoints(asterixis grade, Conn score) were found to be dramatically reduced whencompared to lactulose treatment in patients with HE who receivedlactulose daily for 6 months and then received rifaximin daily for 6months.

The first study was designed to overcome the limitations of previousstudies reported in the literature (e.g., heterogeneous subjectpopulations, small population size, short durations, and insufficientendpoints for mental status).

First, treatment duration was increased to 6 months. This longerduration was planned to allow for a greater number of subjects toexperience an HE episode than if the study was limited to ≦6 weeks.Also, the longer treatment duration provided an opportunity to evaluatethe long-term safety of rifaximin in subjects with chronic hepaticcirrhosis and associated recurrent, overt, episodic HE. The studyinvestigated consequences of HE with respect to patient care andeconomic cost by measuring hospitalizations due to HE episodes as a keysecondary efficacy endpoint.

To evaluate overt HE episodes by using clinically relevant criteria inthe first study and study the second study, mental status impairment wasmeasured by using Conn score (West Haven criteria) and the severity ofneuromotor abnormalities was measured by asterixis grade. The Conn scoreranges from Stage 0 (lack of detectable changes in personality) to Stage4 (coma, decerebrate posturing, dilated pupils). The Conn score is therecommended and widely used gold standard for grading the severity ofimpaired mental status in overt HE. Asterixis (flapping tremor) is aneuromotor symptom of overt HE that increases in severity with worseningneurological impairment.

The control group for the first study received matched placebo tabletsin parallel with rifaximin treatments in the active group. The secondstudy was an ongoing open-label, treatment-extension study to evaluatethe long-term safety of rifaximin 550 mg BID in subjects with a historyof recurrent, episodic, overt HE. In addition to safety measurements,Conn scores and asterixis grades were assessed during the course of thestudy to measure the protective effect of rifaximin against breakthroughovert HE during treatment for up to approximately 1 year in subjects whocompleted up to 6 months of rifaximin treatment in the first study andthen entered the second study; in subjects who received placebo in thefirst study and crossed over to rifaximin treatment in the second study;and in patients with a history of HE who entered the second study as newsubjects.

The dosage regimen used (550 mg BID) was based on past clinicalexperience with rifaximin in patients with HE and other subjectpopulations. In several previous studies, rifaximin was safe andeffective in subjects with HE at a dose of 1200 mg per day with orwithout concomitant lactulose. In a 6-month study of rifaximin versusneomycin (14 days on-treatment and 14 days off-treatment per month),rifaximin 1200 mg/day and neomycin (3 g/day) had comparable efficacy inpatients with HE. Aminoglycoside antibiotics are contraindicated inpatients with advanced liver disease because of the risk ofnephrotoxicity.

An efficacy endpoint was the time to first breakthrough overt HEepisode. A breakthrough overt HE episode was defined as an increase ofConn score to Grade ≧2 (e.g., 0 or 1 to ≧2) or an increase in Conn andasterixis score of 1 grade each for those subjects who entered the studywith a Conn score of 0. Time to breakthrough overt HE episode was theduration from time of first dose of study drug to the first breakthroughovert HE episode. Subjects who completed the study and did notexperience a breakthrough overt HE episode were censored at the time oftheir 6-month visit. Subjects who terminated early for reasons otherthan breakthrough overt HE were contacted at 6 months from randomizationto determine if subjects had experienced a breakthrough overt HE episodeor other outcome (e.g., mortality status); and, if the subject had nobreakthrough overt HE event prior to contact, he/she was censored at thetime of contact. Therefore, complete capture was achieved forbreakthrough overt HE episodes up to 6 months postrandomization.Subjects in the study had ≧2 episodes of overt HE equivalent to Connscore ≧2 within 6 months prior to screening (i.e., subjects haddocumented recurrent, overt HE). At the baseline assessment, subjectswere in remission with a Conn score of 0 or 1. A breakthrough overt HEepisode, as defined above, was a marked deterioration in neurologicalfunction.

Other efficacy endpoints in the first study included, for example:

1. Time to first HE-related hospitalization;2. Time to any increase from baseline in Conn score (mental stategrade);3. Time to any increase from baseline in asterixis grade;4. Mean change from baseline in fatigue domain scores on the CLDQ at endof treatment; and5. Mean change from baseline in venous ammonia concentration at end oftreatment.

Presented herein are the results of the first study and second study.The first study was a double-blind, randomized, placebo-controlled studyevaluating the efficacy and safety of rifaximin 550 mg BID as comparedto placebo. Subjects in remission from demonstrated recurrent, overt,episodic HE associated with chronic, hepatic cirrhosis were randomizedon Day 0 (Visit 2) according to a 1:1 ratio to receive rifaximin 550 mgBID or placebo for 6 months. The primary efficacy endpoint was the timeto breakthrough overt HE. Breakthrough overt HE was defined as anincrease of Conn score to Grade ≧2 (e.g., 0 or 1 to ≧2) or an increasein Conn and asterixis score of 1 grade each for those subjects whoentered the study with a Conn score of 0. Subjects discontinued from thestudy at the time of breakthrough overt HE episode. After participationin the first study, subjects had the option to enroll in the open-label,treatment-extension study (the second study).

A total of 299 subjects were randomized to receive rifaximin (140subjects) or placebo (159 subjects). All randomized subjects received atleast 1 dose of study drug. A total of 251 (84%) (116 [rifaximin], 135[placebo]) subjects completed the study as specified in the protocol(e.g., completed 6 months of treatment or withdrew from the study at thetime of breakthrough overt HE).

Subjects in the study had ≧2 episodes of overt HE equivalent to Connscore ≧2 within 6 months prior to screening (e.g., subjects hadrecurrent, overt HE). At the baseline assessment, subjects were inremission with a Conn score of 0 or 1. A breakthrough overt HE episodewas a marked deterioration in neurological function. Breakthrough overtHE episodes were experienced by 31 of 140 subjects in the rifaximingroup and by 73 of 159 subjects in the placebo group during the 6-monthtreatment period (up to Day 170). Comparison of Kaplan-Meier estimatesof time to breakthrough overt HE between groups showed a protectiveeffect of rifaximin (p<0.0001). These data show that rifaximin treatmentresulted in a 57.9% reduction, when compared with placebo, in the riskof experiencing breakthrough overt HE. Rifaximin treatment results infewer overt HE episodes that may otherwise incapacitate the patient, mayalleviate the burden on family members who are required to care for thepatient, and reduces the burden of hospitalization in this patientpopulation and the healthcare system.

The following prognostic factors were found to be predictors ofbreakthrough overt HE episodes: baseline age (p=0.0160), MELD score(p=0.0003), duration of current verified remission (p=0.1089), andnumber of prior HE episodes (p=0.0022). These data show that rifaximintreatment, resulted in a 60% reduction, when compared with placebo, inthe risk of experiencing a breakthrough overt HE episode during thecourse of this study (p<0.0001).

Time to First HE-Related Hospitalization; and the Frequencies ofHE-Related and all-Cause Hospitalizations

Hepatic encephalopathy-related hospitalizations (hospitalizationdirectly resulting from HE or hospitalization complicated by HE) werereported for 19 of 140 subjects and 36 of 159 subjects in the rifaximinand placebo groups, respectively. Rifaximin had a protective effectagainst HE-related hospitalization during the 6-month treatment period.Subjects in the rifaximin group had a 50% reduction in the risk ofhospitalization due to HE during the 6-month treatment period whencompared with placebo. The HE-related hospitalization rate was 0.38events/PEY in the rifaximin group versus 0.78 event/PEY in the placebogroup.

Hepatic encephalopathy-caused hospitalizations (hospitalization directlyresulting from HE only) were reported for 15 of 140 subjects and 33 of159 subjects in the rifaximin and placebo groups, respectively.Rifaximin had a significant protective effect against HE-causedhospitalization during the 6-month treatment period; hazard ratio in therifaximin group relative to placebo was 0.438 (95% CI: 0.238 to 0.807)(p=0.0064) for the risk of HE-caused hospitalization. Subjects in therifaximin group had a 56% reduction in the risk of hospitalization dueto HE during the 6-month treatment period when compared with placebo.The HE-caused hospitalization rate was 0.30 events/PEY in the rifaximingroup versus 0.72 event/PEY in the placebo group.

All-cause hospitalization was also lower in the rifaximin group (46 of140) than in the placebo group (60 of 159) (30% reduction in therifaximin group compared with placebo). The all cause hospitalizationrate, after normalizing for subject exposure, was 0.90 events/PEY in therifaximin group and 1.26 event/PEY in the placebo group. The HE-relatedhospitalization rate was 0.38 event/PEY in the rifaximin group and 0.78event/PEY in the placebo group. Rifaximin treatment protects againstHE-related hospitalization, thereby improving the quality of life forthe patient and for his/her caregiver, and reducing the economic costrelated to liver cirrhosis and associated HE.

Time to any Increase from Baseline in Conn Score and Time to anyIncrease from Baseline in Asterixis Grade

Protective effects of rifaximin were observed with respect to both ofthese endpoints when analyzed independently; hazard ratio in therifaximin group relative to placebo was 0.463 (95% CI: 0.312 to 0.685)(p<0.0001) for the risk of experiencing an increase in Conn score and0.646 (95% CI: 0.414 to 1.008) (p=0.0523) for the risk of experiencingan increase in asterixis grade during the 6-month treatment period.

Changes from Baseline in Venous Ammonia Levels at End of Treatment

Subjects in the rifaximin group had greater reductions in venous ammonialevels when compared to placebo-treated subjects (p=0.0391).

Venous ammonia levels, a quantitative assessment that is associated withthe CNS effects underlying overt HE, was found to be highly correlatedto the occurrence of breakthrough overt HE as determined by the clinicalevaluation of Conn score (or a combination of Conn score and asterixisgrade).

Tracking of Conn Scores and Asterixis Grades: Changes from Baseline inConn Scores and Asterixis Grades

A favorable treatment effect of rifaximin was observed, when comparedwith placebo, with respect to the proportions of subjects who hadchanges of −1 (improvement) or 0 (no change); or 1, 2, or 3 (worsening)in Conn score from baseline to end of treatment (last postbaselineassessment or assessment at time of breakthrough HE). In the rifaximingroup compared to placebo, higher proportions of subjects experiencedConn score changes of −1 or no change (77.1% versus 53.9%) and lowerproportions of subjects had Conn score changes of 1, 2, 3, or 4. Thus,treatment with rifaximin was more effective than placebo in theprevention of worsening of Conn score (2.46 times versus placebo,p=<0.0001).

For changes from baseline to end of treatment in asterixis grade,significantly higher proportions of subjects in the rifaximin groupversus the placebo group had changes from baseline in asterixis gradesof −2, −1, and 0 (88.5% versus 77.0%), and significantly lowerproportions of subjects had changes of 1, 2, 3, or 4 (11.6% versus23.2%). Thus, treatment with rifaximin was more effective than placeboin the prevention of worsening of asterixis grade (1.92 times versusplacebo, p=0.0262).

Changes from Baseline in CFF Results

Increases in CFF results represent improvement in neurological functionin patients with HE.^(10,11) Subjects in the rifaximin group hadsignificantly greater increases in CFF results from baseline to end oftreatment when compared with placebo. Mean changes (±standard deviation[SD]) in CFF results were 0.945 (±4.75) in the rifaximin group versus0.355 (±4.70) in the placebo group (p=0.0320 for between-groupdifference) Similar to venous ammonia levels, CFF was shown to be highlypredictive of breakthrough HE.

Median exposure to study drug was 168 days (range: 10 to 178) in therifaximin group and 110 days (range: 6 to 176) in the placebo group. Atotal of 64 subjects (33 [rifaximin] and 31 [placebo]) receivedtreatment for 141 to 168 days and 98 subjects (57 [rifaximin] and 41[placebo]) received treatment for >168 days. Duration of exposureresults are consistent with the finding that lower proportions ofsubjects in the rifaximin group than in the placebo group experiencedbreakthrough overt HE resulting in study discontinuation (per protocol,subjects discontinued from the study after breakthrough overt HE).

The percentages of subjects who had treatment-emergent AEs, severeTEAEs, drug-related TEAEs, treatment-emergent SAEs, TEAEs resultingdiscontinuation, and who died were similar between placebo and rifaximingroups. A total of 79.9% of subjects (239 of 299) experienced TEAEsduring the course of the study. The most common TEAEs (e.g., in ≧10% oftotal subjects [combined placebo plus rifaximin]) experienced bysubjects were the following: diarrhea (10.7% [rifaximin] versus 13.2%[placebo]), nausea (14.3% versus 13.2%), peripheral edema (15% versus8.2%), fatigue (12.1% versus 11.3%), dizziness (12.9% versus 8.2%),ascites (11.4% versus 9.4%), and headache (10% versus 10.7%).

The second study is an ongoing open-label, treatment-extension studyevaluating the long-term safety of rifaximin 550 mg BID in subjects witha history of recurrent, overt, episodic HE. All eligible subjects had ahistory of overt HE episodes with a documented severity equivalent toConn score ≧2 within 12 months prior to screening (≧1 qualifying episodewas required), a Conn score of <2 at the baseline assessment, and eitherparticipated in the first study or were new subjects Unlike the firststudy, subjects were not required to withdraw from the study afterexperiencing a breakthrough overt HE episode.

A total of 267 subjects were enrolled and 208 were active at the time ofthe interim clinical cutoff. Additional data were collected for theinterim report up to the time of database freeze.

Conn scores and asterixis grades were assessed during the course of thestudy. Therefore, it was possible to determine time to breakthroughovert HE episode for subjects who completed 6 months of rifaximintreatment in the first study and then entered the second study, subjectswho received placebo in the first study and then started rifaximin inthe second study, and in new subjects who started rifaximin therapy inthe second study. In subjects who took rifaximin for up to 680 days (1.9years), breakthrough overt HE episodes during the treatment period wereexperienced by 72 of 266 subjects (27.1%) overall: 54 of 196 subjects(27.6%) in the new rifaximin group and 18 of 70 subjects (25.7%) in thecontinuing rifaximin group.

Time-to-first-breakthrough HE profiles were similar between therifaximin group in the first study and the new rifaximin group in thesecond study. A durable protective effect of rifaximin was observed insubjects who received rifaximin starting in the first study andcontinuing in the second study (median exposures to rifaximin were 168days in the first study and 253 days in the second study)

A total of 133 of 266 subjects were hospitalized for any cause: 98 inthe new rifaximin group, and 35 in the continuing rifaximin group.Normalizing for subject exposure, this represents a hospitalization rateof 0.60 event/PEY. A total of 59 were hospitalized due HE episodes(e.g., HE-caused). Normalizing for subject exposure, this represents anHE-caused hospitalization rate of 0.29 event/PEY. The low HE-causedhospitalization rate was consistent between rifaximin therapy in thesecond study (0.29 event/PEY) and in the first study rifaximin (0.30event/PEY) at least partly as a result of maintaining remission fromdemonstrated HE in subjects with end-stage liver disease. Tracking ofConn scores and asterixis grades: changes from baseline in Conn scoresand asterixis grades Conn scores were generally maintained or improvedwith rifaximin use up to 18 months. At the last visit, 70.7% of subjects(188 of 266 subjects) had no change and 20.3% (54 of 266) hadimprovements in Conn scores compared with baseline, indicating thatmental status was maintained or improved in the majority of subjects(91%) over the treatment period. Of the 84 subjects (70 new rifaximinand 14 continuing rifaximin) who entered the study with Conn scores of1, 2, or 3 (e.g., those subjects for whom measurable improvement waspossible), 54 subjects (54/84=64.3%) showed a 1-grade (47 subjects;56.0%) or 2-grade (7 subjects; 8.3%) improvement from baseline at thelast visit recorded for the interim analysis. All subjects were capableof worsening over time, and 24/266 subjects (9.0%) did so by 1 or 2grades.

Like Conn scores, asterixis grades were generally maintained or improvedwith rifaximin use up to 18 months. At the last visit, 77.1% of subjects(205 of 266 subjects) had no change and 16.2% (43 of 266) hadimprovements in asterixis scores compared with baseline, indicating thatneuromotor symptoms associated with increasing neurological impairmentwere maintained in 83.3% of subjects over the treatment period. Of the67 subjects (55 new rifaximin and 12 continuing rifaximin) who enteredthe study with asterixis scores of 1, 2, or 3 (e.g., those subjects forwhom improvement was possible), 43 subjects (43/67=64.2%) showed a 1-(34 subjects; 50.7%), 2- (4 subjects; 6.0%), or 3-grade (5 subjects;7.5%) improvement from baseline at the last visit recorded for thisinterim analysis. All subjects were capable of worsening over time, and18/266 subjects (6.8%) did so by 1, 2, or 4 grades; the incidence ofworsening asterixis grades were similar between the new (12/196subjects; 6.1%) and continuing (6/70 subjects; 8.6%) rifaximin groups.

Median exposures in study the second study were 253 days (range: 7 to680) in the new rifaximin group (subjects who received placebo in thefirst study or subjects who did not participate in the first study),265.5 days (range: 10 to 673) in the continuing rifaximin group(subjects who received rifaximin in the first study and the secondstudy), and 255 days (range: 7 to 680) in the all rifaximin group (allsubjects who received rifaximin in the second study). At the time ofthis interim analysis, most subjects had received rifaximin for 6 to <9months (21.4%) or 9 to <12 months (32.3%).

At the time of this interim analysis, TEAEs were reported in 230subjects (86.5%). The most common TEAEs (e.g., in ≧10% of totalsubjects) experienced by subjects were the following: peripheral edema(15.8%); urinary tract infection and nausea (12.8% each); and abdominalpain and ascites (10.5% each). Note that signs and symptoms associatedwith HE were not considered AEs unless they met the definition of anSAE, so the number of subject with HE counted in efficacy analysis (72subjects; 27.1%) is higher than that counted for the safety analyses (57subjects; 21.4%).

Most TEAEs were mild or moderate in intensity, with 40.2% of subjectsexperiencing at least 1 TEAE that was judged by the investigator to besevere. The incidence of TEAEs considered related to study drug wascomparable between the new rifaximin group (7.7%) and the continuingrifaximin group (7.1%). Treatment-emergent SAEs were experienced by47.4% of subjects.

FIG. 1 illustrates Kaplan-Meier estimates of time to first breakthroughovert HE episode by treatment group in the ITT population. Table 18presents Kaplan-Meier estimates of the proportions of subjects whoexperienced breakthrough overt HE over the course of the TreatmentPeriod and results of statistical analyses. Subjects who completed thestudy and did not experience a breakthrough overt HE event were censoredat the time of their 6-month visit. Subjects who terminated early forreasons other than breakthrough overt HE (eg, liver transplant, AE,subject request) were contacted at 6 months from date of randomizationto determine if subjects had experienced a breakthrough overt HE episodeor other outcome (e.g., mortality status). Subjects without breakthroughovert HE were censored at the time of contact or death, whichever wasearlier. Therefore, complete capture was achieved for breakthrough overtHE episodes up to 6 months.

TABLE 18 The First Study: Kaplan-Meier Estimates and StatisticalAnalyses of Time to First Breakthrough Overt HE (up to 6 Months ofTreatment, Day 170) (ITT Population) Placebo (N = 159) Rifaximin (N =140) Probability Probability Treatment Number Cumulative Event of noNumber Cumulative Event of no interval At of number of probabilitybreakthrough At of number of probability breakthrough (days) risk^(a)events^(b) events (SE)^(c) overt HE^(d) risk^(a) events^(b) events(SE)^(c) overt HE^(d)  0 to <28 158 20 20 0.13 (0.03) 1.0000 140 13 130.09 (0.02) 1.0000 28 to <56 137 23 43 0.17 (0.03) 0.8734 126 4 17 0.03(0 02) 0.9071 56 to <84 113 14 57 0.12 (0.03) 0.7262 120 6 23 0.05(0.02) 0.8783  84 to <140 98 10 67 0.10 (0.03) 0.6363 112 7 30 0.06(0.02) 0.8344 140 to <168 84 6 73 0.07 (0.03) 0.5713 98 1 31 0.01 (0.01)0.7820 ≧168 38 0 73 0 0.5305 46 0 31 0 0.7740 Hazard ratio: 0.421^(e)95% CI: (0.275, 0.641) p-value: <0.0001 Table footnotes are on the nextpage. ^(a)Number of subjects at risk during the treatment interval,estimated using the life table method. Assuming that censored cases wereat risk for half of the interval, they only counted for half in figuringthe number at risk. ^(b)Number of events occurring during the treatmentinterval. ^(c)Estimate of the probability of experiencing breakthroughovert HE during the treatment interval. Standard error (SE) estimated byusing Greenwood's formula. ^(d)Estimate of the probability of nobreakthrough overt HE until at least the beginning of the next treatmentinterval. ^(e)Hazard ratio estimate (hazard of breakthrough overt HE inthe rifaximin group compared with the placebo group) determined from theCox proportional hazards model. P-value based on the Score statistic.

Breakthrough overt HE episodes were experienced by 31 of 140 subjects inthe rifaximin group and by 73 of 159 subjects in the placebo groupduring the 6-month period since randomization (up to Day 170).Comparison of Kaplan-Meier estimates of time to breakthrough overt HEbetween groups showed a protective effect of rifaximin (p<0.0001). Thesedata show that rifaximin treatment resulted in a 57.9% reduction, whencompared with placebo, in the risk of experiencing breakthrough overt HEduring the course of this study. Rifaximin treatment results in fewerovert HE episodes that may otherwise incapacitate the patient, mayalleviate the burden on family members who are required to care for thepatient, and reduces the burden of hospitalization in this patientpopulation and the healthcare system.

To investigate the potential effect of prognostic factors onbreakthrough overt HE episode, the following prognostic factors wereexamined:

Sex (male vs. female);

Age;

Race (white vs. non-white);

Analysis Region (North American vs. Russia);

MELD Level;

Conn Score (0 vs. 1);

Diabetes at Baseline (Yes vs. No);

Duration of current verified remission; and

Number of HE Episodes within the past 6 months prior to randomization.

Strong independent predictors of breakthrough overt HE episodes were thebaseline age (p=0.0160), MELD score (p=0.0003), duration of currentverified remission (p=0.1089), and number of prior HE episodes(p=0.0022).

These data show that rifaximin treatment, after adjusting forsignificant prognostic factors, resulted in a 60% reduction, whencompared with placebo, in the risk of experiencing a breakthrough overtHE episode during the course of this study. The most influentialprognostic factors were age (p=0.0315) and baseline MELD score(p=0.0003).

The results indicate that the highly significant protective effect ofrifaximin (p<0.0001) against breakthrough overt HE episodes wasmaintained in the presence of statistically significant competingfactors.

In the second study, median exposures were 253 days (range: 7 to 680) inthe new rifaximin group (subjects who received placebo in the firststudy or subjects who did not participate in the first study), 265.5days (range: 10 to 673) in the continuing rifaximin group (subjects whoreceived rifaximin in the first study and the second study), and 255days (range: 7 to 680) in the all rifaximin group (all subjects whoreceived rifaximin in the second study

In subjects who took rifaximin for up to 680 days (1.9 years),breakthrough overt HE episodes during the treatment period wereexperienced by 72 of 266 subjects (27.1%) overall: 54 of 196 subjects(27.6%) in the new rifaximin group and 18 of 70 subjects (25.7%) in thecontinuing rifaximin group. FIG. 2 compares subjects who participated inthe double-blind, randomized the first study with new rifaximin subjectsin the long-term, open-label study, the second study.

The Kaplan-Meier estimates of time to first breakthrough overt HEepisode were similar between the rifaximin group in the first study andnew rifaximin subjects in the second study. Also, similar proportions ofsubjects had breakthrough overt HE in the rifaximin group of the firststudy (22%, 31 of 140 [rifaximin group]) and in the new rifaximin groupof the second study (27.6%, 54 of 196). Adjusted for exposure, rates ofbreakthrough HE episodes were 0.62 events/PEY in the rifaximin groupfrom the first study compared to 0.38 events/PEY for new rifaximinsubjects in the second study. These data demonstrate that protectionagainst breakthrough overt HE in subjects who received rifaximin wasconsistent between the 2 studies.

Note for FIG. 7, the survival distribution estimate on y-axis representsthe proportion of subjects without breakthrough overt HE.

The first study data on time to first breakthrough overt HE episode areshown for the rifaximin group (small dashes) and the placebo group(straight line). The second study data on time to first breakthroughovert HE episode in the new rifaximin group are shown in large dashes.

In FIG. 8, the first study placebo subjects were followed after theycrossed over to rifaximin therapy in the second study. Breakthroughovert HE was experienced by 15 of 82 during rifaximin treatment versus39 of 82 during placebo treatment. A striking protective effect ofrifaximin was observed in the comparison of Kaplan-Meier estimates oftime to first breakthrough overt HE between placebo experience in thefirst study and rifaximin experience in the second study. The hazardratio of rifaximin to placebo was 0.302 (95% CI: 0.166 to 0.549,p<0.0001 for between group difference in relative risk). This resultrepresents 70% reduction in risk of experiencing breakthrough overt HEduring rifaximin treatment in the second study when compared with theirprior placebo experience in the first study.

Note for FIG. 8, the survival distribution estimate on y-axis representsthe proportion of subjects without breakthrough overt HE. the firststudy data on time to first breakthrough overt HE episode are shown inthe left panel for the placebo group. The right panel shows time tofirst breakthrough overt HE in the second study among the first studyplacebo subjects (n=82) who crossed over to rifaximin therapy in thesecond study. The vertical line between the left and right panels marksthe end of the double-blind study and start of the open-label study.

FIG. 9 illustrates time to first HE-related hospitalization (e.g.,hospitalization directly resulting from HE or hospitalization caused byHE) by treatment group in the ITT population in the first study. Table19 presents estimates of the proportions of subjects who had their firstHE-related hospitalization over the course of the Treatment Period andresults of statistical analyses. Subjects who discontinued prior tohospitalization due to HE and prior to completion of the 6-monthtreatment period were censored at the time of discontinuation. Hepaticencephalopathy-related hospitalizations were reported for 19 of 140subjects and 36 of 159 subjects in the rifaximin and placebo groups,respectively. Rifaximin had a protective effect against HE-relatedhospitalization during the 6-month treatment period; hazard ratio in therifaximin group relative to placebo was 0.500 (95% CI: 0.287 to 0.873)(p=0.0129) for the risk of HE-related hospitalization. This hazard ratiorepresents a 50% reduction, when compared with placebo, in the risk ofhospitalization due to HE during the 6-month treatment period.Consistent with these results, the HE-related hospitalization rate was51% lower (0.38 event/PEY, rifaximin versus 0.78 event/PEY, placebo) inthe rifaximin group in the first study, after normalization to exposure.

Note for FIG. 9, the survival distribution estimate on y-axis representsthe proportion of subjects without HE-related hospitalization. Dashedline represents rifaximin group and solid line represents placebo group.Open circles and open triangles represent censored subjects. Subjectswho discontinued prior to hospitalization due to HE and prior tocompletion of the 6-month treatment period were censored at the time ofdiscontinuation. Hepatic encephalopathy-related hospitalization wasrecorded on the HE-related hospitalization CRF.

TABLE 19 The First Study: Kaplan-Meier Estimates and StatisticalAnalyses of Time to First HE-Related Hospitalization (up to 6 Months ofTreatment, Day 170) (ITT Population) Placebo (N = 159) Rifaximin (N =140) Probability Probability of no of no Treatment Number CumulativeEvent HE-related Number Cumulative Event HE-related interval At ofnumber of probability hospital- At of number of probability hospital-(days) risk^(a) events^(b) events (SE)^(c) ization^(d) risk^(a)events^(b) events^(b) (SE)^(c) ization^(d)  0 to <28 155 11 11 0.07(0.02) 1.0000 139 4 4 0.03 (0.01) 1.0000 28 to <56 132 12 23 0.09 (0.03)0.9288 130 4 8 0.03 (0.02) 0.9711 56 to <84 108 7 30 0.06 (0.02) 0.8440119 4 12 0.03 (0.02) 0.9411  84 to <140 88 4 34 0.05 (0.02) 0.7893 106 517 0.05 (0.02) 0.9094 140 to <168 72 2 36 0.03 (0.02) 0.7535 92 2 190.02 (0.02) 0.8665 ≧168 34 0 36 0 0.7525 43 0 19 0 0.8475 Abbreviations:CI = confidence interval; SE = standard error. ^(a)Number of subjects atrisk during the treatment interval, estimated using the life tablemethod. Assuming that censored cases were at risk for half of theinterval, they only counted for half in figuring the number at risk.^(b)Number of events occurring during the treatment interval.^(c)Estimate of the probability of experiencing HE-relatedhospitalization during the treatment interval. Standard error (SE)estimated by using Greenwood's formula. ^(d)Estimate of the probabilityof no HE-related hospitalization until at least the beginning of thenext treatment interval. ^(e)Hazard ratio estimate (hazard of HE-relatedhospitalization in the rifaximin group compared with the placebo group)determined from the Cox proportional hazards model. P-value based on theScore statistic.

The effect of rifaximin therapy on HE-caused hospitalizations (e.g.,hospitalization directly resulting from HE only) was also determined.FIG. 5 illustrates time to first HE-caused hospitalizations by treatmentgroup in the first study.

Hepatic encephalopathy-caused hospitalizations were reported for 15 of140 subjects and 33 of 159 subjects in the rifaximin and placebo groups,respectively. Rifaximin had a significant protective effect againstHE-caused hospitalization during the 6-month treatment period; hazardratio in the rifaximin group relative to placebo was 0.438 (95% CI:0.238 to 0.807) (p=0.0064) for the risk of HE-caused hospitalization.Subjects in the rifaximin group had a 56% reduction in the risk ofhospitalization due to HE during the 6-month treatment period whencompared with placebo. The HE-caused hospitalization rate was 0.30events/PEY in the rifaximin group versus 0.72 event/PEY in the placebogroup.

Note for FIG. 10, the survival distribution estimate on y-axisrepresents the proportion of subjects without HE-causedhospitalizations. Dashed line represents rifaximin group and solid linerepresents placebo group. Open circles and open triangles representcensored subjects. Subjects who discontinued prior to hospitalizationwere censored at the time of discontinuation.

The effect of rifaximin therapy on all-cause hospitalizations was alsodetermined. In the double-blind the first study, 46 of 140 rifaximinsubjects and 60 of 159 placebo subjects were hospitalized due to anySAE. The risk of all-cause hospitalization was reduced by 30% in therifaximin group when compared to placebo (p=0.0793 for between-groupdifference in relative risk). The all-cause hospitalization rate was0.92 events/PEY in the rifaximin group versus 1.31 event/PEY in theplacebo group. These data demonstrated that rifaximin treatment reducedthe burden of HE-related/caused hospitalization when compared to placebotreatment in the first study. Also, a low HE-related/causedhospitalization rate was consistently observed during rifaximin therapyin the first study (0.38 event/PEY) and in the second study (0.29event/PEY), at least partly as a result of maintaining remission fromdemonstrated HE in subjects with end-stage liver disease.

FIG. 11 illustrates time to any increase from baseline in Conn score bytreatment group in the ITT population. Table 20 presents estimates ofthe proportions of subjects who had any increase in Conn score over thecourse of the Treatment Period and results of statistical analyses.Subjects who discontinued prior to experiencing an increase in Connscore and prior to completion of the 6-month treatment period werecensored at the time of discontinuation. By evaluating the time to anyincrease from baseline in Conn score, it was possible to compare theearliest worsening in mental status between subjects in the rifaximinand placebo treatment groups, even if the worsening did not reach thedefinition of breakthrough HE (eg, increase in Conn score from 0 to 1).Increases in Conn score were reported for 37 of 140 subjects and 77 of159 subjects in the rifaximin and placebo groups, respectively. A highlysignificant protective effect of rifaximin was observed; hazard ratio inthe rifaximin group relative to placebo was 0.463 (95% CI: 0.312 to0.685) (p<0.0001) for the risk of experiencing an increase in Conn score(e.g., worsening in mental status) during the 6-month treatment period.

TABLE 20 The First Study: Kaplan-Meier Estimates and StatisticalAnalyses of Time to First Increase in Conn Score (up to 6 Months ofTreatment, Day 170) (ITT Population) Placebo (N = 159) Rifaximin (N =340) Probability Probability Treatment Number Cumulative Event of noNumber Cumulative Event of no interval At of number of probabilityincrease in At of number of probability increase in (days) risk^(a)events^(b) events (SE)^(c) Conn score^(d) risk^(a) events^(b) events(SE)^(c) Conn score^(d)  0 to <28 156 26 26 0.17 (0.03) 1.0000 139 17 170.012 (0.03)  1.0000 28 to <56 125 21 47 0.17 (0.03) 0.8333 119 5 220.04 (0.02) 0.8777 56 to <84 100 15 62 0.15 (0.04) 0.6928 109 9 31 0.08(0.03) 0.8407  84 to <140 80 10 72 0.13 (0.04) 0.5883 94 5 36 0.05(0.02) 0.7713 140 to <168 62 5 77 0.08 (0.03) 0.5143 79 0 36 0 0.7302≧168 27 0 77 0 0.4729 37 1 37 0.03 (0.03) 0.7302 Abbreviations: CI =confidence interval; SE = standard error. ^(a)Number of subjects at riskduring the treatment interval, estimated using the life table method.^(b)Number of events occurring during the treatment interval. Assumingthat censored cases were at risk for half of the interval, they onlycounted for half in figuring the number at risk. ^(c)Kaplan-Meierestimate of the probability of experiencing an increase in Conn scoreduring the treatment interval. Standard error (SE) estimated by usingGreenwood's formula. ^(d)Estimate of the probability of no increase inConn score until at least the beginning of the next treatment interval.^(e)Hazard ratio estimate (hazard of experiencing an increase in Connscore in the rifaximin group compared with the placebo group) determinedfrom the Cox proportional hazards model. P-value based on the Scorestatistic.

FIG. 12 illustrates time to any increase from baseline in asterixisgrade by treatment group in the ITT population in the first study. Table21 presents estimates of the proportions of subjects who had anyincrease in asterixis grade over the course of the Treatment Period andresults of statistical analyses. Subjects who discontinued prior toexperiencing an increase in asterixis grade and prior to completion ofthe 6-month treatment period were censored at the time ofdiscontinuation.

By evaluating the time to any increase from baseline in asterixis grade,it was possible to compare the earliest worsening in neuromotorfunctioning between subjects in the rifaximin and placebo treatmentgroups. Increases in asterixis grade were reported for 32 of 140subjects and 50 of 159 subjects in the rifaximin and placebo groups,respectively. A protective effect of rifaximin against an increase inasterixis grade (e.g., worsening in neuromotor functioning) was observedthat showed a trend toward statistical significance; hazard ratio in therifaximin group relative to placebo was 0.646 (95% CI: 0.414 to 1.008)(p=0.0523) for the risk of experiencing an increase in asterixis gradeduring the 6-month treatment period.

TABLE 21 The First Study: Kaplan-Meier Estimates and StatisticalAnalyses of Time to First Increase in Asterixis Grade (up to 6 Months ofTreatment, Day 170) (ITT Population) Placebo (N = 159) Rifaximin (N =140) Probability Probability of no of no Treatment Number CumulativeEvent increase in Number Cumulative Event increase in interval At ofnumber of probability asterixis At of number of probability asterixis(days) risk^(a) events^(b) events (SE)^(c) grade^(d) risk^(a) events^(b)events (SE)^(c) grade^(d)  0 to <28 154 20 20 0.13 (0.03) 1.0000 137 1313 0.10 (0.03) 1.0000 28 to <56 120 15 35 0.13 (0.03) 0.8697 116 7 200.06 (0.02) 0.9048 56 to <84 91 4 39 0.04 (0.02) 0.7610 101 7 27 0.07(0.03) 0.8499  84 to <140 76 6 45 0.08 (0.03) 0.7275 87 3 30 0.03 (0.02)0.7910 140 to <168 61 4 49 0.07 (0.03) 0.6701 74 1 31 0.01 (0.01) 0.7637≧168 27 1 50 0.04 (0.04) 0.6262 34 1 32 0.03 (0.03) 0.7534Abbreviations: CI = confidence interval; SE = standard error. ^(a)Numberof subjects at risk during the treatment interval, estimated using thelife table method. Assuming that censored cases were at risk for half ofthe interval, they only counted for half in figuring the number at risk.^(b)Number of events occurring during the treatment interval.^(c)Estimate of the probability of experiencing an increase in asterixisgrade during the treatment interval. Standard error (SE) estimated byusing Greenwood's formula. ^(d)Estimate of the probability of noincrease in asterixis grade until at least the beginning of the nexttreatment interval. ^(e)Hazard ratio estimate (hazard of experiencing anincrease in asterixis grade in the rifaximin group compared with theplacebo group) determined from the Cox proportional hazards model.P-value based on the Score statistic.Subjects ranked their level of fatigue by using a 7-point scale from theworst response (1, high degree of fatigue) the best response (7, minimalfatigue) Minimal differences between placebo and rifaximin groups wereobserved in the changes from baseline in CLDQ fatigue scores. Mean (SD)fatigue scores were 3.34 (1.406) versus 3.28 (1.326) at baseline and3.51 (1.529) versus 3.57 (1.527) in the placebo and rifaximin groups,respectively. Because of altered mental and neuromotor status, it wasnot possible for subjects to complete the CLDQ assessment during anovert HE breakthrough episode.

Table 22 summarizes changes from baseline to end of treatment in venousammonia level by treatment group in the first study.

In the first study, venous ammonia levels were highly variable over thecourse of the study. However, subjects in the rifaximin group hadsignificantly greater reductions in venous ammonia levels when comparedto placebo-treated subjects (p=0.0391). Venous ammonia levels, aquantitative assessment that is associated with the CNS effectsunderlying overt HE, was shown to be highly predictive of the occurrenceof breakthrough overt HE as determined by the clinical evaluation ofConn score (or a combination of Conn score and asterixis grade), therebyunderscoring the reliability and clinical relevance of the primaryefficacy measure. The significant correlation of the primary efficacyendpoint to a venous ammonia levels demonstrates the reliability andclinical relevance of the primary efficacy measure in the first study.

TABLE 22 The First Study: Mean (SD) Changes from Baseline in VenousAmmonia Level by Treatment Group (ITT Population) Placebo Rifaximin N =159 N = 140 (μg/dL) (μg/dL) Baseline n = 146 n = 132 Mean (SD) ammonialevel 90.3 (52.48) 87.9 (47.76) End of treatment n = 141 n = 132 Mean(SD) ammonia level 88.4 (45.75) 83.9 (45.02) Change from baseline to endof treatment n = 131 n = 125 Mean (SD) change in ammonia level −0.3(58.13) −5.7 (46.77) Note: Baseline value was the last available valueprior to first dose of study drug, and end of treatment value was thelast available post-baseline value during the treatment period.

The Second Study

In the second study, Conn scores were generally maintained or improvedwith rifaximin use up to 18 months. At the last visit, 70.7% of subjects(188 of 266 subjects) had no change and 20.3% (54 of 266) hadimprovements in Conn scores compared with baseline, indicating thatmental status was maintained or improved in the majority of subjects(91%) over the treatment period. Like Conn scores, asterixis grades weregenerally maintained or improved with rifaximin use up to 18 months. Atthe last visit, 77.1% of subjects (205 of 266 subjects) had no changeand 16.2% (43 of 266) had improvements in asterixis scores compared withbaseline, indicating that neuromotor symptoms associated with increasingneurological impairment were maintained in 83.3% of subjects over thetreatment period. The last visit for the second study is the last visitrecorded for the interim analysis.

Maintenance or improvement in Conn scores were observed for >85% ofsubjects during rifaximin treatment for up to 840 days; mean (±SD)exposure for all rifaximin experience was 273.8 (160.92) days (exposureresults are present in detail in the ISS, Module 5.3.5.3.2). A total of65.5% of subjects (220 of 337) had no change in Conn score and 21.1% (71of 337) had improvements in Conn score from baseline to last visit.Similarly, maintenance or improvements in asterixis grades were observedfor >90% of subjects during rifaximin treatment. No change from baselinein asterixis grade was reported for 75.2% of subjects (252 of 337), and17.3% had improvements.

Of the 118 subjects who entered the study with a Conn score of ≧1, e.g.,those subjects for whom improvement was possible, 62.2% (71 of 118)showed an improvement from baseline to Conn score 0 at last assessment.Also, of the 99 subjects who entered with an asterixis grade of ≧1, iethose subjects for whom improvement in asterixis grade was possible,58.6% (58 of 99) showed improvement in asterixis grade from baseline toend of study.

Changes from baseline in Conn scores and asterixis grades to last visitwere similar among new rifaximin subjects in the second study (e.g.,started rifaximin in 3002), continuing rifaximin subjects (e.g.,received rifaximin in the first study and in the second study), and allrifaximin experience subjects (e.g., received rifaximin in the firststudy or in the second study).

These results support those from the first study, in which treatmentwith rifaximin was significantly more effective than placebo in theprevention of worsening of Conn score (2.46 times versus placebo,p<0.0001) and in the prevention of worsening of asterixis grade (1.92times versus placebo, p=0.0262).

Changes from Baseline in CFF Results (the First Study)

Increases in CFF results represent improvement in neurological functionin patients with HE. Subjects in the rifaximin group had significantlygreater increases in CFF results from baseline to end of treatment whencompared with placebo (Table 23). Mean changes (±SD) in CFF results were0.945 (±4.75) in the rifaximin group versus 0.355 (±4.70) in the placebogroup (p=0.0320 for between-group difference).

Similar to the correlation for venous ammonia levels, there was a strongcorrelation between the quantitative assessment of CFF results and theoccurrence of breakthrough overt HE.

TABLE 23 Mean (SD) Changes from Baseline in CFF Test Results byTreatment Group (ITT Population) Placebo Rifaximin N = 159 N = 140 (Hz)(Hz) Baseline n = 159 n = 140 Mean (SD) CFF result 37.41 (6.03) 36.90(5.47) End of treatment n = 155 n = 139 Mean (SD) CFF result 37.60(5.98) 37.81 (4.88) Change from baseline to end of treatment n = 155 n =139 Mean (SD) change in CFF result 0.355 (4.70) 0.945 (4.75) Note:Baseline value was the last available value prior to first dose of studydrug, and end of treatment value was the last available post-baselinevalue during the treatment period.

A retrospective chart review was performed for 145 patients with HE whoreceived lactulose 30 mL twice daily for ≧6 months followed by treatmentwith rifaximin 400 mg 3 times/day for ≧6 months. Dramatic differenceswere observed in favor of rifaximin treatment. Compliance of ≧75% wassignificantly better during rifaximin treatment than during lactulosetreatment; 92% versus 31% of patients received ≧75% of scheduledrifaximin and lactulose doses, respectively. Total number ofhospitalizations, duration of hospitalizations, HE endpoints, and costof therapy were compared between the 2 treatment regimens. Significantlyfewer hospitalizations (0.5 versus 1.6) and days hospitalized (2.5versus 7.3 days) were reported for rifaximin treatment versus lactulosetreatment (p<0.001), and hospitalization charges per patient were$14,222 compared with $56,635 during rifaximin and lactulose treatments,respectively.

With respect to HE endpoints at the end of the treatment periods,asterixis was reported for 63% (rifaximin) versus 93% (lactulose) ofpatients (p<0.001), and Conn scores of 3 or 4 were observed for 6%(rifaximin) versus 25% (lactulose) (p<0.001). In addition, significantlymore patients had diarrhea, flatulence, and abdominal pain duringlactulose therapy than during rifaximin therapy (p<0.001).

Hospitalizations and cost of therapy were analyzed in a chart review of39 liver transplant patients who presented with HE Conn scores of 2during the interval from January 2004 to November 2005. Twenty-fourpatients were treated with lactulose and 15 were treated with rifaximin.Nineteen hospitalizations were reported for the lactulose group and 3hospitalizations for the rifaximin group. The average length of stay wassignificantly shorter in the rifaximin group than in the lactulose group(3.5 days [range, 3-4] versus 5.0 days [range, 3 to 10] [p<0.001]). Theaverage annual total cost of treatment (hospitalization, emergency roomvisit, and drug cost) per patient was $7958 for the rifaximin group and$13,285 for the lactulose group. Although the cost of rifaximin wassubstantially higher than the cost of lactulose, total cost of treatment(hospitalization plus drug cost) was 1.67-fold higher in patients whowere treated with lactulose.

Durability of Rifaximin Treatment Effect

Data from the second study provide information on the long-termdurability of rifaximin for the protection against breakthrough overt HEepisodes. Rifaximin treated subjects from the first study who were inremission at the end of the first study (6 months treatment) werefollowed during open-label study the second study (n=60). Time to firstbreakthrough HE episode is shown for the rifaximin rollover subjects(the first study plus the second study) and the first study placebosubjects in FIG. 15. The incidence of breakthrough overt HE in theserollover rifaximin subjects was compared to placebo subjects in thefirst study. The incidence of breakthrough HE episode for rifaximinsubjects was dramatically lower than the first study placebo group(ratio of rollover rifaximin to placebo was 0.0797 after adjusting forexposure time, p<0.0001 for difference between rifaximin and placebo.

These results demonstrated that rifaximin had a durable protectiveeffect beginning in the first study and continuing in the second study(median exposures to rifaximin were 168 days in the first study and 253days in the second study).

Note for FIG. 13, the survival distribution estimate on y-axisrepresents the proportion of subjects without breakthrough overt HE.Dashed lines represents rifaximin treated subjects from the first studywho were in remission at the end of the first study (6 months treatment)and were followed during open-label study the second study (n=60), andsolid line represents the placebo group in the first study. The verticalline marks the end of the double-blind study and start of the open-labelstudy. Open circles represent censored subjects in the first studyplacebo group and open triangles represent censored subjects in thecontinuing rifaximin group. Subjects who discontinued prior to the firstbreakthrough overt HE episode were censored at the time ofdiscontinuation.

Unlike the first study, in which subjects were discontinued from thestudy after experiencing their first breakthrough overt HE episode,subjects had the option of continuing rifaximin therapy in the secondstudy after experiencing breakthrough overt HE. Therefore, the incidenceof breakthrough overt HE over time during rifaximin therapy wasevaluated. Table 24 presents breakthrough overt HE episodes by totalnumber of HE episodes during the course of the study.

In the all rifaximin group, 27.1% of subjects (72 of 266) had ≧1breakthrough overt HE episode. Of the 72 subjects with breakthrough HE,most had 1 (44 subjects) or 2 (18 subjects) episodes. Ten subjects had 3or more breakthrough HE episodes in the second study.

TABLE 24 the second study: Breakthrough Overt HE Episodes by Number ofRepeat Episodes New Continuing All Rifaximin Rifaximin Rifaximin N = 196N = 70 N = 266 n (%) n (%) n (%) Subjects with ≧1 breakthrough 54 (27.6)18 (25.7) 72 (27.1) overt HE episode Total number of HE episodes^(a)during the study:  1 34 (17.3) 10 (14.3) 44 (16.5)  2 12 (6.1)  6 (8.6)18 (6.8)   3 4 (2.0) 0 4 (1.5)  4 1 (0.5) 1 (1.4) 2 (0.8)  5 1 (0.5) 0 1(0.4)  6 0 1 (1.4) 1 (0.4) 10 2 (1.0) 0 2 (0.8) Abbreviation: HE =hepatic encephalopathy ^(a)Number of HE episodes. Subjects were countedonly once for each number of overt HE episodes. For example, if asubject experienced 3 episodes, he/she was included in the row showing 3episodes only, and was not also counted in the rows for 2 and 1episodes.

Effect of Rifaximin on the Incidence of Overt HE Episodes (HE Burden)

The effect of rifaximin therapy on the incidence of overt HE episodes(e.g., burden of HE), the numbers of HE episodes in the first study orthe second study were compared to the numbers of HE episodes in theabsence of rifaximin therapy. The 6-month interval prior to the firststudy or the 12-month interval prior to the second study was comparedagainst rifaximin therapy in either study. The time of participation inthe first study did not reflect experience in the absence of rifaximintherapy, therefore, for subjects who rolled over to the second studywithout an HE episode in the first study, the 12-month interval prior tothe second study was used for comparison. Most subjects in the secondstudy (152 of 266) were also in the first study. Overt HE episodes inthe second study were combined with the first study because, unlike thefirst study, subjects in the second study had the option of remaining onrifaximin after experiencing their first breakthrough HE episode. Thenumbers of overt HE episodes experienced during the 6-month or 12-monthintervals prior to the first study or prior to the second study wereknown. While 30.8% of subjects had >2 HE episodes during the 6-month or12-month interval prior to rifaximin therapy, only 3.6% of subjectshad >2 HE episodes during rifaximin therapy for up to 840 days (medianexposure=253 days [˜8 months]) in the first study plus the second study.This difference in the incidence of HE episodes while subjects werereceiving rifaximin when compared to the absence of rifaximin therapysuggests a strong effect of rifaximin in relieving the burden of overtHE episodes in patients with recurrent, overt HE associated severe liverdisease.

Hepatic encephalopathy is a serious, rare, complex, episodic,neuropsychiatric syndrome associated with advanced liver disease.Hepatic encephalopathy is a formidable burden on the patient, his/herfamily, and the healthcare system. Overt HE episodes are debilitating,render the patient incapable of self-care, and frequently result inhospitalization. Rifaximin has been granted orphan drug status for theHE indication because the disease is serious and chronicallydebilitating (further described in Section 1.1), and there is a lowincidence of HE in the general population. Also, there is an unmetmedical need for patients with HE because of limitations of the currentstandard of care.

Without wishing to be bound by any specific scientific theories, it isbelieved that the mechanism of action of rifaximin depends on theinhibition of DNA-dependent RNA polymerase of the target microorganisms,leading to the suppression of initiation of chain formation in RNAsynthesis. Rifaximin has a lower rate of fecal eradication of pathogenscompared with other commonly used antibacterial drugs and causes minimalalterations in gut flora suggesting that rifaximin has a differentmechanism of action than other commonly used drugs in enteric bacterialinfection, such as the fluoroquinolones. The antibacterial properties ofrifaximin appear to result from bactericidal activity at rifaximinconcentrations greater than or equal to the MIC, and from alterations inbacterial morphology and physiological functioning, which have beenobserved at sub-MIC concentrations.

It was unexpectedly discovered herein, that the risk of the developmentof antibiotic resistance is low during chronic treatment with rifaximinwhen compared to other systemic antibiotics such as neomycin. The lowrisk of antibiotic resistance during rifaximin therapy is likely due tothe fact that resistance to rifaximin is not plasmid-mediated butinstead requires a stable mutation in host cell DNA; therefore,dissemination of resistance and cross-resistance to other antibiotics byplasmid-based mechanisms are eliminated. Also, bacteria at sites outsideof the GI tract are not exposed to appreciable selective pressurebecause of negligible systemic concentrations of rifaximin Additionally,microbiological data from a study of patients with ulcerative colitiswho were receiving high doses of rifaximin showed thatrifaximin-resistant bacterial colonies generated during in vivo exposureto rifaximin were unstable and susceptibility returned after a briefperiod of treatment interruption.

Rifaximin treatment results in fewer overt HE episodes that mayotherwise incapacitate the patient, may alleviate the burden on familymembers who are required to care for the patient, and reduces the burdenof hospitalization in this patient population and the healthcare system.The following are results from the second study with respect to time tofirst breakthrough overt HE episode:

The protective effect was reproducible: the time to first breakthroughovert HE episode results were similar between the rifaximin group in thefirst study and new rifaximin subjects in the second study; and 22% and27.6% had breakthrough overt HE in the first study rifaximin group andthe second study new rifaximin group, respectively. Adjusted forexposure, rates of breakthrough HE episodes were 0.62 events/PEY in therifaximin group from the first study compared to 0.38 events/PEY for newrifaximin subjects in the second study. These data demonstrate thatprotection against breakthrough overt HE in subjects who receivedrifaximin was consistent between the 2 studies. Additionally, when thefirst study placebo subjects crossed over to rifaximin therapy byentering the second study, a striking protective effect of rifaximin wasobserved in the comparison of Kaplan-Meier estimates of time to firstbreakthrough overt HE between placebo experience in the first study andrifaximin experience in the second study. The hazard ratio of rifaximinto placebo was 0.302 (95% CI: 0.166 to 0.549, p<0.0001 for between groupdifference in relative risk). This result represents 70% reduction inrisk of experiencing breakthrough overt HE during rifaximin treatment inthe second study when compared with their prior placebo experience inthe first study. This reduction took place in spite of the aging andpresumably progressing nature of the population with chronic liverdisease.

The protective effect was durable: the Kaplan-Meier estimate oftime-to-first breakthrough HE demonstrated long-term maintenance ofremission from breakthrough HE when rifaximin subjects in remissionafter participation in the first study were followed in the second study(up to 680 days of rifaximin therapy; median exposure durations were 168days in the first study and 253 days in the second study). The incidenceof breakthrough HE episode for these rifaximin subjects relative to thefirst study placebo was dramatically low, an indication of fewerbreakthrough HE episodes with rifaximin treatment (p<0.0001 fordifference in relative risk between rifaximin and placebo).

Results for other efficacy endpoints also demonstrated statisticallysignificant protective effects of rifaximin. In the first study, theanalysis of time to first HE-related hospitalization (e.g.,hospitalization directly resulting from HE or hospitalizationcomplicated by HE) demonstrated that the reduction in risk ofhospitalization due to HE was 50% in the rifaximin group, when comparedwith placebo, during the 6-month treatment period (p=0.0129 forbetween-group difference in relative risk). In the first study, the riskof HE-caused hospitalization (e.g., hospitalization directly resultingfrom HE only) was reduced by 56% (p=0.0064 for between-group differencein relative risk), and the risk of all-cause hospitalization was reducedby 30% in the rifaximin group compared with the placebo group (p=0.0793for between-group difference in relative risk). In the first study, therisk of all-cause hospitalization rate was reduced by 30% in therifaximin group when compared to placebo (p=0.0793 for between-groupdifference in relative risk). The all-cause hospitalization rate was0.92 events/PEY in the rifaximin group versus 1.31 event/PEY in theplacebo group.

In the second study, the low HE-caused hospitalization rate wasmaintained at rates consistent with those in the first study: HE-causedhospitalization rate was 0.29 event/PEY and all cause hospitalization inthe second study was 0.66 event/PEY. The consistently lowHE-related/HE-caused hospitalization rate in rifaximin-treated subjectsin the first study and in the second study was at least partly a resultof maintaining remission from demonstrated HE in subjects with end-stageliver disease.

The invention now being fully described, it will be apparent to one ofordinary skill in the art that many changes and modifications can bemade thereto without departing from the spirit or scope of the appendedclaims.

What is claimed is:
 1. A method of treating or preventing hepaticencephalopathy (HE) comprising administering to a subject in needthereof a gastrointestinal (GI) specific antibiotic.
 2. The method ofclaim 1, wherein the GI specific antibiotic maintains remission of HE inthe subject.
 3. A method of decreasing a subject's risk of a hepaticencephalopathy (HE) breakthrough episode comprising administering a GIspecific antibiotic to a subject suffering from HE.
 4. The method ofclaim 3, wherein the risk of the episode for subjects having a last HEepisode equal to, or greater than, 90 days prior to the administrationis reduced by about 58%.
 5. The method of claim 3, wherein the risk ofthe episode for subjects having a last HE episode equal to, or greaterthan, 90 days prior to the administration is reduced by between about30% to 70%.
 6. The method of claim 3, wherein the risk of the episodefor subjects having a last HE episode greater than 90 days prior to theadministration is decreased by between about 60%.
 7. The method of claim3, wherein the risk of the episode for subjects having a last HE episodegreater than 90 days prior to the administration is decreased by betweenabout 2% to 80%.
 8. The method of claim 3, wherein the risk of theepisode for subjects having two or fewer HE episodes in the six monthsprior to the administration is reduced by about 56%.
 9. The method ofclaim 3, wherein the risk of the episode for subjects having 2 or fewerHE episodes in the six months prior to administration is reduced bybetween about 20% to 70%.
 10. The method of claim 3, wherein the risk ofthe episode for subjects having greater than two HE episodes in the sixmonths prior to rifaximin administration is reduced by about 63%. 11.The method of claim 3, wherein the risk of the episode for subjectshaving greater than two HE episodes in the six months prior to theadministration is reduced by between about 30% to about 80%.
 12. Themethod of claim 3, wherein the risk of the episode is decreased by about58%.
 13. The method of claim 3, wherein the risk of the episode isdecreased by between about 40% to about 70%.
 14. A method of maintainingremission of HE in a subject comprising administering a GI specificantibiotic to a subject suffering from HE.
 15. A method of reducing thefrequency of hospitalization visits by an HE patient, comprisingadministering a GI specific antibiotic to a subject suffering from HE.16. The method of claim 15, wherein administration of rifaximin reduceshospitalization frequency by about 48%.
 17. The method of claim 15,wherein administration of rifaximin reduces hospitalization frequency byfrom between about 13% to about 69%.
 18. The method of claim 1, 3, 14,or 15 wherein the GI specific antibiotic comprises a rifamycin classantibiotic.
 19. The method of claim 1, 3, 14, or 15, wherein the GIspecific antibiotic comprises rifaximin.
 20. The method of claim 19,wherein 550 mg of rifaximin is administered to the subject two times perday (BID).
 21. The method of claim 19, wherein 275 mg of rifaximin isadministered to the subject four times per day.
 22. The method of claim19, wherein 275 mg of rifaximin is administered to the subject as twodosage forms two times per day.
 23. The method of claim 1, 3, 14, or 15,wherein the GI specific antibiotic is administered to the subject forsix months.
 24. The method of claim 1, 3, 14, or 15, wherein the GIspecific antibiotic is administered to the subject for one year.
 25. Themethod of claim 1, 3, 14, or 15, wherein the GI specific antibiotic isadministered to the subject for two to three years.
 26. The method ofclaim 1, 3, 14, or 15, wherein the GI specific antibiotic isadministered daily to the subject until the subject's death.
 27. Themethod of claim 1, 3, 14, or 15, wherein a Conn score of the subject isimproved over baseline following administration of a GI specificantibiotic.
 28. The method of claim 1, 3, 14, or 15, wherein a qualityof life (QoL) measurement is improved from baseline followingadministration of a GI specific antibiotic.
 29. The method of claim 1,3, 14, or 15, further comprising administering lactulose.
 30. The methodof claim 1, 3, 14, or 15, further comprising administering one or moreof align, alinia, Lactulose, pentasa, cholestyramine, sandostatin,vancomycin, lactose, amitiza, flagyl, zegerid, prevacid, or miralax. 31.The method of claim 1, 3, 14, or 15, wherein a Conn score (mental stategrade) of the subject decreases.
 32. The method of claim 1, 3, 14, or15, wherein time to a Conn score increase from baseline for the subjectis increased.
 33. The method of claim 32, wherein the delay in time toincrease in Conn score of the subject is increased by about 54%.
 34. Themethod of claim 32, wherein the delay in time to increase in Conn scoreis increased between about 30% to about 70%.
 35. The method of claim 1,3, 14, or 15, wherein administration of the GI specific antibioticprevents an increase in Conn score of the subject.
 36. The method ofclaim 1, 3, 14, or 15, wherein there is an increase of time to anincrease from baseline in an asterixis grade of the subject.
 37. Themethod of claim 1, 3, 14, or 15, wherein there is a delay in the time toincrease in asterixis grade.
 38. The method of claim 1, 3, 14, or 15,wherein there is an increase in time to a first HE-relatedhospitalization of the subject.
 39. The method of claim 1, 3, 14, or 15,wherein there is an increase in the time to development of spontaneousbacterial peritonitis (SBP) of the subject.
 40. The method of claim 1,3, 14, or 15, wherein there is a decrease in blood ammonia concentrationfrom baseline after administration of the GI specific antibiotic of thesubject.
 41. The method of claim 40, wherein the decrease in bloodammonia concentration from baseline to 170 days is about 6 μg/dL. 42.The method of claim 1, 3, 14, or 15, wherein there is an increase incritical flicker frequency values from baseline after administration ofa GI specific antibiotic to the subject.
 43. The method of claim 1, 3,14, or 15, wherein there is a decrease in daily lactulose consumptionfrom baseline over time after administration with the GI specificantibiotic to the subject.
 44. The method of claim 43, wherein thedecrease in daily lactulose consumption is from between about 7 doses oflactulose to about 2 doses of lactulose.
 45. The method of claim 44,wherein lactulose use of the subject initially increases from baseline.46. The method of claim 45, wherein the initial increase in lactuloseuse is from between about 1 and about 30 days.
 47. The method of claim1, 3, 14, or 15, wherein there is a shift in baseline in Conn scoresover time after administration of the GI specific antibiotic to thesubject.
 48. The method of claim 47, wherein the shift in baseline inConn scores is from between about 1 to about
 2. 49. The method of claim1, 3, 14, or 15, wherein there is a shift from baseline in asterixisgrades over time after administration of the GI specific antibiotic tothe subject.
 50. The method of claim 1, 3, 14, or 15, wherein there is achange from baseline in Chronic Liver Disease Questionnaire (CLDQ)scores over time after administration of the GI specific antibiotic tothe subject.
 51. The method of claim 1, 3, 14, or 15, wherein there is achange from baseline in Epworth Sleepiness Scale scores over time afteradministration of the GI specific antibiotic to the subject.
 52. Themethod of claim 1, 3, 14, or 15, wherein subjects having a meld level ofbetween about 1 to 24 respond to treatment with GI specific antibiotics.53. The method of claim 1, 3, 14, or 15, wherein subjects having a meldlevel less than or equal to ten respond to treatment with GI specificantibiotics.
 54. The method of claim 1, 3, 14, or 15, wherein subjectshaving a meld level between 11 and 18 respond to treatment with GIspecific antibiotics.
 55. The method of claim 1, 3, 14, or 15, whereinsubjects having a meld level between 19 and 24 respond to treatment withGI specific antibiotics.
 56. A method of treating or preventing HEcomprising administering 550 mg of rifaximin for more than 28 days. 57.A method of decreasing lactulose use in a subject, comprising:administering rifaximin to a subject daily that is being treated withlactulose; and tapering lactulose consumption.
 58. The method of claim57, wherein tapering comprises reducing lactulose consumption by 1, 2,3, 4, 5, 6 or more unit dose cups of lactulose from a baseline level.59. The method of claim 57, wherein tapering comprises reducinglactulose consumption by 5, 10, 15, 20, 25, 30, 34, 40, 45, 50, 55, 60,65, or 70 g lactulose from a baseline level.
 60. The method of claim 57,wherein tapering comprises reducing lactulose consumption.
 61. Themethod of claim 57, wherein the tapering is from a baseline to noconsumption of lactulose.
 62. A method of maintaining remission of HE ina subject comprising administering 550 mg of rifaximin BID.
 63. A methodof increasing time to hospitalization for HE comprising, administeringto a subject 550 mg of rifaximin two times per day (BID).
 64. A methodof treating a patient suffering from hepatic encephalopathy, comprising:advising a patient suffering from hepatic encephalopathy thatadministration of rifaximin may induce cytochrome P450 activity; andadministering rifaximin to the patient in order to treat the hepaticencephalopathy.
 65. The method of claim 64, wherein the cytochrome P450activity is cytochrome P450 3A4 (CYP3A4) activity.
 66. The method ofclaim 64, wherein administering rifaximin comprises administering 1100mg of rifaximin per day to the patient.
 67. The method of claim 64,wherein administering rifaximin comprises administering rifaximin twiceper day to the patient.
 68. The method of claim 64, further comprisingadvising a patient that is taking a cytochrome P450 substrate to seekadditional medical guidance.
 69. The method of claim 64, whereinadvising the patient comprises providing the patient with writtenmaterial.
 70. The method of claim 69, wherein the written material is ona drug label.
 71. A method of administering rifaximin as a treatment forhepatic encephalopathy, comprising: advising a health care worker thatpatients being administered rifaximin as a treatment for hepaticencephalopathy may induce cytochrome P450 activity; and administeringthe rifaximin to the patient in order to treat the hepaticencephalopathy.
 72. The method of claim 71, wherein the healthcareworker is a doctor, a nurse, or a pharmacist.
 73. The method of claim71, wherein advising the health care worker comprises providing thehealth care worker with written advice.
 74. The method of claim 71,wherein the cytochrome P450 activity is cytochrome P450 3A4 (CYP3A4)activity.
 75. A method of increasing the time between breakthroughevents for a patient suffering from hepatic encephalopathy, comprisingadministering to the patient an effective amount of rifaximin thatextends the time between hepatic encephalopathy breakthrough events. 76.The method of claim 75, wherein the time between breakthrough events forthe patient is extended to greater than six months.
 77. The method ofclaim 75, wherein the time between breakthrough events for the patientis extended to greater than twelve months.
 78. The method of claim 75,wherein the effective amount of rifaximin comprises 1100 mg of rifaximinper day.
 79. A method of lowering the risk of antibacterial resistancewhen treating chronically with an antibacterial composition, comprisingadministering rifaximin chronically to treat irritable bowel syndrome,travelers' diarrhea, small intestinal bacterial overgrowth, Crohn'sdisease, pancreatitis, pancreatic insufficiency, peritonitis, hepaticencephalopathy, pouchitis, infectious diarrhea, inflammatory boweldisease, diverticular disease, Clostridium, C. difficile disease, H.pylori infection, enteritis and colitis and other related conditions. Amethod of alleviating caretaker burden comprising, administeringrifaximin to a subject in need thereof to treat hepatic encephalopathy.80. A method of reducing hospitalization rate comprising, administeringrifaximin to a subject in need thereof to treat hepatic encephalopathy.81. The method of claim 80, wherein the subject is less likely to haveimproper nutrition compared to a subject not administered rifaximin. 82.The method of claim 80, wherein the rate of non-adherence to therapy isdecreased in the subject compared to a subject not administeredrifaximin.
 83. The method of claim 80, wherein the subject is lesslikely to further escalate into more severe symptoms compared to a to asubject not administered rifaximin.
 84. The method of claim 80, whereinthe more severe symptoms comprise one or more of increased somnolence,gross disorientation and stupor.
 85. A method of reducing the economiccost related to liver cirrhosis and/or associated HE comprisingadministering a subject suffering from HE a rifamycin class antibiotic.86. A method of increasing the mental status in a subject comprising,administering rifaximin to the subject, thereby increasing the mentalstatus in a subject.
 87. The method of claim 86, wherein the mentalstatus is measured using a Conn Score.
 88. The method of claim 86,wherein the mental status is measured using asterixis grade.
 89. Themethod of decreasing the number of overt HE episodes in a subjectcomprising, administering rifaximin to the subject, thereby decreasingthe number of overt HE episodes.
 90. The method of claim 89, wherein thesubject has liver disease.
 91. The method of claim 89, wherein thesubject has decreased numbers of overt HE episodes for at least 2 years.92. The method of claim 89, wherein the effective amount of rifaximincomprises 1650 mg of rifaximin per day.
 93. A method for increasing thechance of survival of a subject having HE, comprising administering tothe subject rifaximin, thereby increasing the chance of survival for thesubject.
 94. A method of administering rifaximin as a treatment forhepatic encephalopathy, comprising: advising a health care worker thatrifaximin does not increase the risk of QT prolongation; andadministering the rifaximin to the patient in order to treat the hepaticencephalopathy.
 95. The method of claim 94, further comprising the stepof advising the health care worker that there is a greater than 30 folddifference in the hERG 1050 value and the unbound Cmax value.
 94. Amethod of administering rifaximin as a treatment for hepaticencephalopathy, comprising: advising a health care worker that rifaximindoes not significantly alter the C_(max), AUC_(0-t), or AUC_(0∞) ofmidazolam; and administering the rifaximin to the patient in order totreat the hepatic encephalopathy.
 95. The method of claim 94, whereinthe subject is administered 1650 mg/day of rifaximin.
 96. The method ofclaim 95, wherein the subject is administered 1650 mg/day of rifaximinfor at least 7 days.